the red dead redemption online is massive, you have the option to either jump right into the free roam which lets you ride around the map, join posse's,take down gangs and compete in different sub games like land grab.
the other great aspect of the multiplayer is you can choose a bunch of different game modes like gang matches, co-op missions,objective missions and if you own can play the undead horde mode which is level after level of undead attacking you till your overrun.
one of my fav modes is the gambling modes where you can play either poker,blackjack or my fav liars dice.
also there are horse races you can compete in all the while earning cash to use in the multiplayer.
i would strongly suggest buying the game of the year red dead redemption i did and i love it, you will get frustrated by some of the people that play online but it's worth it,the number of rdr players is still VERY HIGH so you can almost always find someone to play with/against.