Short answers, pulled from the story.
Operation Bodyguard was the Allied deception strategy deployed before the 1944 invasion of northwest Europe. Its goal was to mislead the German high command about the timing and location of the invasion, with a particular focus on making the Pas-de-Calais appear to be the main invasion target rather than Normandy.
The name came from a remark Winston Churchill made to Joseph Stalin at the Tehran Conference in late 1943: "In wartime, truth is so precious that she should always be attended by a bodyguard of lies." The strategy was formally approved under that name on Christmas Day 1943.
Hitler delayed redeploying the Fifteenth Army from Pas-de-Calais to Normandy for nearly seven weeks after the D-Day landings. The original goal of Bodyguard had been to hold back German reinforcements for at least 14 days, so the actual outcome significantly exceeded the planners' target.
FUSAG, the fictional 1st U.S. Army Group, was a notional Allied invasion force created as part of Operation Fortitude South to threaten the Pas-de-Calais. U.S. General George Patton was placed at its head because German commanders, particularly Rommel, held him in high regard and considered him a credible commander for a major invasion force.
Operation Ironside used three double agents codenamed Tate, Bronx and Garbo. Juan Pujol Garcia, the Spanish double agent codenamed Garbo, also played a key role on D-Day itself, transmitting British High Command's message that the Normandy landings were a diversion.
General Omar Bradley described Operation Bodyguard as the single biggest hoax of the war in his memoirs. Thaddeus Holt's 2004 book The Deceivers credits the success of its main component, Fortitude, partly to the earlier Cockade operation, which gave the London Controlling Section a rehearsal for the larger deception.