If someone is bisexual, it means they are attracted to both men and women. Lots of people are attracted to both sexes at some point in their life, however for those who know that they are truly bisexual, it is a permanent thing. Some are in happy monogamous relationships, others have lots of partners of both sexes. Some bisexuals are happily married bringing up children. Some bisexuals are single, some are celibate.
Bisexuality is about who you are attracted to, not just who you have sex with.