How does a crush feel?

Tbh I'm 99% sure I'm aromantic And if you don't know what that means. It basically means I feel little to no romantic attraction to anybody At all But I can still feel sexual. Sexual attraction, unlike Ace people But anyways back to the main point i really don't understand how you can just look at someone and have a crush on them and be like. Oh I want to spend my life with this person or oh I want them to be my boyfriend or girlfriend. It just doesn't make sense? Also You guys lose interest so fast like you were literally just saying you wanted to marry this person