I'm listening to a podcast with an interview about The Agency, and I realized I have no idea how an MMO works in terms of story progression, for any MMO not just this one.

I like just playing a game from start to finish, doing missions, and following a story.

Do I have to always play with the same people to keep going through missions (in any game, not just the Agency) or will the game see where I am in the story, then find other people to place me with that are also about to do the same mission, and then I just play with them?

I've never played an MMO and The Agency and DC University Online look really cool, I just don't understand how you'd progress through the game if you just want to play through the story.