JP = Job Points. You get them for completing missions. The more JP a player has, the more missions they have done this session. When you log out, they reset to 0. They're supposed to affect what jobs you get and how fast you get them, but I've never really looked into it.
They determine who wins a playlist. EVERYthing else is speculation. At least I've never seen proof of any other effect. --- Remember: IamI3rian told ya Wish I could play Skyrim again for the first time. -AflockOfHippies
They're a representative of who has been the luckiest at not getting pointlessly forced into different sessions or timed out into GTA5, mostly. --- I am snazzier, hot, hot rant. Warily slight as. Croak rush, OK? Weirder, almighty make out. ::)