In the US House there are 16 committees. There are ranking chairs and minority chairs for each committee, along with committee members. The ranking chairs are for the majority, in this Congress the Republicans. The minority chairs are, of course, for the Dems. The chairs dictate subjects, schedule and rules. The Republicans choose their chairs, the Democrats vote for theirs. AOC is running for the minority chair of the Oversight Committee, which is the main investigative committee of Congress. They took a straw vote today and AOC lost, but all of the Dems will vote tomorrow.