Thank you, that is just what we need here.
When a minority in the Senate opposes the passage of a bill that the majority will pass if it comes to a vote, they sometimes filibuster. The Senate rules say that anyone can speak as long as she or he wishes, and as long as a Senator is speaking, they cannot call for a vote. Sometimes these opposition Senators just take turns speaking as long as they can to delay the vote: this is called a filibuster. It doesn't matter what they are talking about, they can just keep talking.
The only way the Senators can be stopped from speaking and forced to allow the bill to be voted on, is for at least 60 of the 100 Senators to vote for "closure". If President Obama has at least 60 Senators on his side, they will always be able to end the filibuster: he has a "filibuster proof majority." If he had 51-59 Senators on his side, he would still have a majority, but it would not be filibuster proof.
Thomas Tompion has written a more succinct explanation as I was writing this, but I will post this anyway.