LGBT+

First I could be wrong but wasn't it originally LGBT I keep seeing people adding on extra letters im guessing more groups and forms of sexual identity have emerged? I feel bad saying this but I don't get it? like what is the actual difference between gender fluid and bi? Also what are all the extra letters and I did try to look this up but I don't really know we're to start also I have identified as bi for a long time now tho Ive heard that there's an identity were your just neutral to either (I think gender fluid) and im like oh but isn't that just really bi? thanks for the info and comments 😎

update: I think I meant pansexual