Cloture is needed in the U.S. Senate on a controversial bill or nomination in order to close debate and allow a vote on the bill or nomination to occur. If there is no cloture, then debate never ends and the bill cannot become law or the nominee cannot be confirmed.
Explained another way, cloture is the only procedure by which the Senate can vote to place a time limit on consideration of a bill or other matter, and thereby overcome a filibuster. Under the cloture rule (Rule XXII), the Senate may limit consideration of a pending matter to 30 additional hours, but only by vote of three-fifths of the full Senate, normally 60 votes.
President Woodrow Wilson demanded a way for the Senate to limit internal debate on bills during World War I. Accordingly, on March 8, 1917, during a special session of the 65th Congress, the Senate ended its traditional rule of allowing unlimited debate by adopting a "cloture rule" that limited debate if 2/3rds of Senators agreed. If cloture was thereby attained, then each member could speak for only one additional hour before voting on the final bill.
In 1975, the Senate reduced the required number of votes for cloture from 2/3rds to only three-fifths of members, which amounts to 60 Senators needed to invoke cloture.