Short answers, pulled from the story.
W. Mark Felt, the former Deputy Director of the Federal Bureau of Investigation, was the real identity of Deep Throat revealed on the 31st of May 2005. This disclosure came through a Vanity Fair article written by John D. O'Connor, who stated that Felt, then aged ninety-one and suffering from dementia, was the man Woodward and Bernstein had relied upon.
The Watergate break-in occurred on the 17th of June 1972 when five men were arrested inside the offices of the Democratic National Committee at the Watergate Complex in Washington, D.C. These men were in possession of $2,300, plastic gloves, burglary tools, and electronic devices intended to be planted in the Democratic Committee offices.
Woodward and Felt met in an underground garage located at 1401 Wilson Boulevard in Rosslyn, Virginia, often at 2:00 a.m. on the bottom level just over the Key Bridge. They met there six times between October 1972 and November 1973, using the garage as an anonymous secure location to discuss the Watergate scandal.
Mark Felt decided to leak information to Bob Woodward because he believed he was protecting the FBI by pushing information from FBI files to the public to build pressure on Nixon. Felt had nothing but contempt for the Nixon White House and their efforts to manipulate the Bureau for political reasons after being passed over for the directorship.
Woodward and Deep Throat communicated to arrange their secret meetings by using a flowerpot with a red flag on the balcony of Woodward's apartment to signal a meeting desire. When Deep Throat wanted a meeting, he would make special marks on page 20 of Woodward's copy of The New York Times, circling the page number and drawing clock hands to indicate the hour.