Angels (Hebrew word malak; Greek word angelos): intelligent beings existing beyond the space and time dimensions of the universe, subject to spiritual laws but not
  necessarily to natural laws. One third, the fallen angels or demons, are in rebellion against God. The remaining two-thirds bear responsibility for service to God and can, at His biding,
 make contact with humans in the space and time dimensions of the universe.
 
Spirit beings (Humans), manifest a capacity that not even the most highly intelligent soulish animals possess, the ability to discern dimensions beyond the ones we physically experience.
 We may even interact and dialogue, knowingly or not, with spiritual beings from beyond our  physically experienced dimensions. According to the Bible, human beings may sometimes be allowed to see, hear, interact and dialogue with angels, mistaking  them for
 humans. In the book of Hebrews we are exhorted, "Do not forget to entertain strangers, for by so doing some people have entertained angels without knowing it." (Hebrews 13:2, NIV.).
 
1 Sometimes people know, or come to recognize, angels as messengers from the spiritual,
 or extra-dimensional realm, as we see in accounts of Abraham's, Lot's, and Daniels
 interactions with angels.2 Because we are spiritual beings, we humans can pray. Through
  prayer we can cross the space-time manifold of the cosmos and converse with God
 in His extra-dimensional realm. Because prayer is extra-dimensional in its reach, it must be
  considered the most powerful capacity God has made available to us in our current dimensional context. Prayer is so powerful, it comes with special cautions and restrictions
 on its use.
ANGELS
3 The angels we see in paintings and sculptures typically have feminine or childlike features, golden halos, and wings ranging from tiny to grandiose. Many artistic portrayals  more
 closely resemble the traditional image of Cupid than they do the biblical description of angels. The Bible tells us that they are mighty4 and holy.5 It says they are mightier than we humans are.
 
6 They are so swift as to defy the laws of physics.7 They are subject neither to decay nor to death. They can be visible or invisible to humans.8 In most biblically recorded cases of their
  appearance on Earth, the people who saw and heard them responded with terror. The following account by Daniel illustrates an angel's impact:
 
"As I was standing on the bank of the great river, the Tigris, I look up and there before me
was a man dressed in linen, with a belt of the finest gold around his waist. His body was
like chrysolite, his face like lightning, his eyes like flaming torches, his arms and legs like
the gleam of burnished bronze, and his voice like the sound of a multitude. I, Daniel, was
the only one who saw the vision; the men with me did not see it, but such terror
overwhelmed them that they fled and hid themselves. So I was left alone, gazing at this
great vision; I had no strength left, my face turned deathly pale and I was helpless."(Daniel
10:4-8, NIV.)

Daniel then explains that when the angel started speaking, he (Daniel) passed out, and the angel had to help him to his feet. The angel's purpose in coming to Daniel was to give him
 a message about the future, to let him know what is written in "the Book of Truth," as the angel  called it. The angel also reported his intense conflict with a fallen angel, specifically with the demon who held some measure of authority over Persia. This demon  had the power to detain the angel for twenty-one days.
 

From these biblical accounts and others, we learn that angels' capacities reflect their existence in at least some of God's dimensions outside the four of the universe. Compared
  to God, however, angels are limited. The Bible indicates that God alone is omnipotent,
omniscient, and omnipresent. Angels are not.9 Though they have access to more dimensions than we  humans do, they occupy a limited dimensionality, as we do. Though they are able to exercise  extraordinary power,10 they are created beings, as we are, incapable of creating any other beings.11 Unlike humans, they do not marry or procreate,12 though some Bible scholars interpret a few passages of Scripture as suggesting that fallen angels in one  way or
another, and for a limited time, demonstrated the capacity to produce "mutant" offspring through sexual relations with human women.

 Cherubim, Seraphim, and Archangels
13 God apparently endowed certain angelic beings with power and authority above others. Though many "ranks" of angels may exist,14 the Bible mentions but three. The highest order
 appears to be the cherubim. Cherubim (Hebrew word kerub, singular, -im, plural; Greek word cheroubim): a special order of angelic beings with a unique role in directing and
expressing worship toward God. Satan, identified as the most powerful and exalted of all the angels - before his rebellion - was a cherub.15 No beings in all Scripture, other than God Himself, give observers a more difficult descriptive task. Depictions by the prophet Ezekiel16 and the apostle John17 represent arduous attempts to portray extra-dimensional features that far surpass what we humans can comprehend or imagine and far surpass the capacities and attributes shared by the lower ranks of angels. The cherubim alone are entrusted with certain tasks in protecting God's glory and holiness and in proclaiming His grace. What all these tasks entail we cannot yet begin to
imagine. Seraphim is a Hebrew term for "burning ones."18 This title probably refers neither to fire as we know it nor to the consuming judgment. Rather, it expresses the passionate devotion of a particular order of angelic beings to praise and proclaim all creation. God's holiness and majesty. Though these angels, too, are awesome to behold, they pose at least a little less difficulty for humans to describe than do the cherubim.19 Archangels (Greek word archangelos): angels of exalted rank and power, sent by God to carry out special assignments. It is possible that God created more than one archangel.20 However, only
one, Michael, is mentioned by name in the Bible.21 His specific role is perhaps most comparable to that of a military leader. He is the commander who leads the angelic host against Satan's demonic forces. Michael's ultimate victory over Satan 22 suggests that his powers and abilities may at least approximate Satan's.

Roles Now and Later
When we read of the awesome powers and attributes angels possess, we may wonder why God would describe us as "a little lower than the heavenly beings" or "angels."23 Though the dimensionality and capacities of the angels supersede ours by what seems a vast margin, we have the opportunity and capacity to comprehend certain spiritual realities that mystify angels.24 In the life that continues past our physical death, we humans who choose to worship Christ will be assigned as "judges" (leaders) and teachers of the angels.25 We will not necessarily gain power advantage over angels. Our role as judges over them has more to do with direction and authority than with power. For now, one of the roles God has assigned to angels is to help provide for our protection. The more we need, due to age, other dependency factors, and spiritual circumstances, the more we get.26 God also deploys angels to perform supernatural acts of service on behalf of those individuals who devote their lives fully to spreading the gospel (the good news of what Jesus has offered to humanity) and equipping other to do the same.27

References:

Ross Hugh, Ph. D., "Beyond The Cosmos" NavPress, 1996 Reasons to Believe, p. 118, 123, 126-128, 205 Hugh Ross's References: -1. Hebrews 13:2, NIV. An example of communication where the form of the angel could not be perceived by the human participant is given in Job 4:12-17
 
 

-2. Genesis 18:1-19:29, Daniel 10:1-21, NIV. -3. Jeremiah 7:16, 14:10-12; 1 Corinthians 14:1-40; James 5:13-20; 1 John 5:14-17, NIV. -4. Psalm 103:20; 2 Thessalonians 1:7, NIV. -5. Revelation 14:10, NIV. -6. 2 Peter 2:11, NIV. -7. Matthew 26:53, NIV. -7. Matthew 26:53, NIV. -8. 2 Kings 2:9-12, 6:15-18, NIV. -9. Isaiah 42:8, 43:10-11, 44:6, 45:5,22-24, NIV. -10. Revelation 7:2-3, 16:8-9, NIV> -11. Isaiah 44:24, Colossians 1:16-17, Revelation 4:11, NIV. -12. Matthew 22:30, NIV. -13. Genesis 6:2-4, Jude 6-8, NIV. A fuller exposition on this interpretation is given in my paper, Sons of God.....Who Are They? (Pasadena, Calif.: Reasons To Believe, 1985). -14. Ephesians 3:10, 6:12; Colossians 1:16, 2:15, NIV. -15. Ezekiel 28:12-17, NIV. -16. Ezekiel 1,10, NIV. -17. Revelation 4:6-8, NIV. -18. Harris, Archer, and Waltke, p.884. -19. Isaiah 6:2-7, NIV. -20. Daniel 10:13, NIV. -21. Daniel 10:21, Jude 9, NIV. -22. Revelation 12:7-9, NIV. -23. Psalm 8:4-5, Hebrews 2:6-7, NIV. -24. Ephesians 1:8-10, 3:10; 1 Peter 1:12, NIV. -25. Daniel 7:18-27, 1 Corinthians 6:2-3, NIV. -26. Matthew 18:10, NIV. -27. Hebrews 1:14, NIV.