Since Buffy wasn't killed by the Master, like the prophecies
perceived to be the future, not everyone in the world found
out she hadn't died. A new slayer was called, making it two
slayers instead of one. Kendra was called from her people(who
think this to be a very great honor) and train to go replace
Buffy and watch the Hellmouth. Although, when Kendra got there,
she discovered Buffy hadn't died. The two slayers learned from
each other. "I knew 'I'm the only one!' was just an attention
getter!"~Xander.
Kendra died at the end of season 2, and Faith was called as the slayer to replace her. Faith and Buffy were pretty buddy buddy for a while, until Faith accidently killed a person. Faith turned to the darkside and partnered up with evil, leaving Buffy and the gang behind. Even thou Faith is working for the Evil Mayor of Sunnydale, she is still a slayer.