What exactly do you do for your job?

A bit of everything. Currently, I do work for the support team, Scrolls, and Minecraft Realms. I'm not the team lead for support (that's Hampus now), I guess the closest title (which we don't really use) would be project admin. I still write the help articles, am the admin for our @MojangSupport account, and coordinate a lot of info between HQ and Support in terms of upcoming releases. If we're going to put out something that people will use, I try to think how they will break it and how we will support it. I still answer customer emails and tweets, just not nearly as much as I used to.
For the Scrolls team, I manage the @ScrollsGame Twitter account and the Facebook account. I post new information and coordinate with both the developers and the community managers. I sort of fell into that job because I applied for the community manager job and had social media experience, but it turned out that the two guys they picked up were much more skilled with some of the in-depth parts of the job, like running Scrolls tournaments, etc. I still wanted to help, so social media went to me. I also coordinate Scrolls releases and questions with the support team.
Lastly, for Minecraft Realms, I use my community contacts to find cool survival maps, adventure maps, or minigames, and get them loaded into the game. I work with mapmakers to ensure that their maps are both right for Realms and that they function perfectly. I personally QA every map by playing it most or all of the way through, sometimes this is a few minutes for minigames, and much longer for maps like Diversity 2.
That was a long answer. Basically, I talk/write a lot about how people use our games.