Questions on "end game"

[StephenMB]

So been focused hard on 2 groups. 5 Pals and War/Dru/H/H/H - Should hit 120 this weekend at the latest. Now again, I am brand new to this game and it occurred to me last night, I have no idea what I am going to do at 120 or what I SHOULD do might be more appropriate.

What I know that I need to do is "gear up" - Just focusing on leveling through outdoor quests the last few weeks has me substantially lower than other people my level, so certainly at 120 I will be very gimpy. What is the best way to really getting the higher end gear for my teams?

I see a lot of people talking about keys, M+ levels, dailies, weekly chests ... none of which I have the slightest idea what they really are because I haven't done any of them.... so I am like George Costanza and writing things off on his taxes. I say all those but really no idea what they are or how to do them. Are they separate things or all the same thing? I just know asking this question in Blizzard forums and asking here will yield entirely different results, so asking here

Any other stuff you guys do at 120 that would benefit me I would appreciate. Thanks all!