The Senate may not vote on a bill until the debate is finished. It used to be where that someone would stand on the floor of the Senate for hours and read a phone book or something like that.
That action is still an available course of action by today’s Senators.
But about 90 years ago the Senate changed that. Not only did debate have to end, but sixty senators had to agree that it had ended. This changed the Congress.
By failing to show up for work, the Senators could block the bill on any legislation. The Democrats have used this more than the Republicans in blocking Bush’s judicial nominations.
See “cloture” in wikipedia. They did a rather fair job in describing it.
So, you have two votes:
1) Stop debate and bring the bill to a vote
2) Vote on the bill’s passage
That was a REAL filibuster, not the "lite" version we have today where the majority leader figures the bill won't be considered until there are 60 votes secured as necessary for cloture to stop a real filibuster. None of them has the fortitude to hold the floor in the time honored fashion.