When they start to interact, they get more and more information about well they get along, the kind of things the other person enjoys etc. This is a fun process if you're attracted to someone, and you can get more and more interested in them.

This applies equally to getting to know someone in a non-romantic context, and in fact fairly well describes my excitement at meeting someone who I think might be a potential friend. Why is it sometimes feelings of love instead of friendship?

(Note that this is in the context of not really understanding the difference between a friend-relationship and a romantic-relationship.)