What does it mean if a very talkative guy knows you but doesn't talk much to you whereas he talks a lot to people he knows and jokes around a lot?

could mean a few things either you are very quiet around him and he may not know what to say to you.

could be he likes you and doesn't know what to say,

could be he doesn't feel he conects with you.

i would say just see if he makes eye contact and start to talk to him or smile he may just speak to you then