Red Dead Redemption 2 has been out for about a month now, which is hopefully enough time for everyone to plow through the dozens of hours of single-player gameplay (and the porn remake), because the online portion of the game is coming on November 27th. 

For those who bought the "ultimate edition" of the game, they will have access to the Red Dead Redemption 2: Online beta tomorrow, with release dates for everyone else staggered and opening for all on the 30th. As far as what actually happens differently in RDR2 Online as opposed to the single player experience, read Rockstar's vague statement below:

With the gameplay of Red Dead Redemption 2 as its foundation, Red Dead Onlinetransforms the vast and deeply detailed landscapes, cities, towns, and habitats of Red Dead Redemption 2 into a new, living online world ready to be shared by multiple players. Create and customize your character, tailor your abilities to suit your play style, and head out into a new frontier full of things to experience.

Explore this huge world solo or with friends. Form or join a posse to ride with up to seven players; gather around the fire at your camp; head out hunting or fishing; visit bustling towns; battle enemy gangs and attack their hideouts; hunt for treasure; take on missions and interact with familiar characters from across the five states; or fight against other outlaws in both spontaneous skirmishes and pitched set-piece battles; compete with other players or whole posses in open world challenges and much more. (The Verge)