To be fond of something is to like it. Sports fans are fond of sports. Oddly, this adjective can also mean foolish and silly.
We're all fond of some things and people: the things and people we like. Being fond can mean anything from liking something a little ("I'm fond of that band") to be extremely, almost absurdly interested in something ("He's a little too fond of football"). This word sometimes implies foolishness and absurdity: almost like you love something so much that you've lost your mind. But usually being fond is a good thing: it just means you enjoy something.