It is sex with someone you know for a long time. Not an emotional "love" connection, just someone you care about as a friend only and it is just sex for mutual pleasure.
If you can't fuck your friends than who can you fuck a total stranger you know nothing about? Better and safer to have a bed buddy.
It is sex with a friend whom you've known and care about but not as emotional, love interest relationship. Someone that can maintain the separation of sex and being in love.
As long as both partners understand the boundaries it can provide a lifetime of fond positive memories.
, Booty call
, Safe Sex
, fuck buddy
, Friends with Benefits