When we talk about the LGBTQ+ community, we often think about people who identify as lesbian, gay, queer, or trans — and we breeze right past the bisexual part. That's a problem, and one that reflects how many people refuse to acknowledge that bisexuality exists at all, called "bi erasure." Surveys suggest that people who identify as bisexual actually make up more than half the LGBTQ+ community, so clearly, bisexuality is A Thing.
The most widely accepted definition of "bisexuality" is "the potential to be attracted — romantically or sexually — to people of more than one sex or gender, not necessarily at the same time, not necessarily in the same way, and not necessarily to the same degree." Of course, everyone who identifies as bisexual has a different relationship to the word, because everyone's experiences coming to terms with their own sexuality are different.