The Demi part means that you're not romantically attracted to
people unless you form a strong bond with them. Therefore, when you see random
people or whatever, you don't feel attracted to them unless you fall for their personality after you get to know them. So, you don't really get "crushes"
like most
people do.
The Panromantic part means that if/when you fall for someone, they could be any gender, meaning that you could be attracted to any gender or gender identity.
The Asexual part means that you're never attracted to people sexually and you don't desire sexual interactions like making out, having sex, that stuff.