What is love? I don't really know myself.

I've seen people say they love eachother and end up leaving eachother by their own accord. I know family love but even that can stop for some people as sad as it is. Is love meant to last but made temporary for some? Or is it supposed to be temporary and people just find a way to make it last throughout their lifetime.

It honestly scares me that this could happen. I don't even know the first thing about love with another person. I see everyone in my school easily going into relationships one after the other and I don't really get it. I get highschool is where it happens a lot but I just don't see how it happens that easily, even the freshmen (which makes me worry a bit) get into these relationships and it only leaves me with one question.

How does love work?