1) The Senate is a majority body, but it requires a 60 vote (i.e. 60%) threshold to cut off debate and force a vote on a bill; otherwise, debate continues indefinitely.
2) In practice, this obviously can lead to the Senate becoming a supermajority body if filibusters are routinely exercised. In the last 5-10 years, this has become the case. For instance, this is an example of a bill that "failed" despite receiving a 54-46 vote.
http://www.washingtonpost.com/blogs/post-politics/wp/2013/04...
3) This rule change would only apply to presidential appointments. The 60-vote threshold would remain in place for other bills.