What was it like and why did you start having it?
Pictures can describe a crush better than words :P
Feels like holding a bag of rocks filled with fuck you written on one and another saying well to bad. The you just drop the load on someone else
It gets to feel extremely annoying and unpleasant if the crush doesn't seem to have any interest in you, which causes your mind to keep working overtime to come up with ideas on how to impress them and get their attention.
Unfortunately I don't know any other feeling asides from this because my crushes have never really been interested in me beyond the friend level.
It feels good to be around them, but if you're a cuck with anxiety, and thus can't talk to them, let alone confess, it's hellish.