they share ‘content’ they deem their audience will find funny or noteworthy or even makeuthink.
gifs, meme pictures, short videos that would’ve been rejected by you’ve been framed in 1993 for not being funny enough, that sort of stuff.
They create veeeeeeeeerryy little of their own stuff, if anything at all. I haven’t seen a lot of it recently but when it first became popular, it was targeted at/by stereotypical lad students into ‘banter’ and there were all sorts of horrible things on there. Apparently it toned down towards the end of its life.
Their revenue is/was generated by people clicking on said content, sharing it on FB etc, and the Ad revenue that is generated from that.