The core story content is single player only. The rest is multiplayer, but unlike Destiny there’s nothing that requires you to form your own group outside of the game, and all the gameplay is designed in such a way that you really don’t need to communicate. You can basically just turn on public matchmaking and get a bunch of humans who might as well be bots for all you’ll have to actually interact with them.

You can play all the content solo if you want to, but the difficulty might get a bit much, especially starting out (there are also certain game modes / mission types that really lean on having a full group).