Short answers, pulled from the story.
Operation Bodyguard received final orders on December 6th and was officially approved on Christmas Day 1943. Winston Churchill suggested the title during discussions with Joseph Stalin at the Tehran conference in late November 1943.
The primary goal of Operation Bodyguard was to mislead German intelligence regarding both the timing and location of the Allied invasion. Planners aimed to make the Pas-de-Calais region appear as the main target instead of Normandy while keeping German reinforcements tied up for at least fourteen days after D-Day.
Fortitude South focused on the Pas-de-Calais by deploying the fictional First United States Army Group under General George Patton. Rommel heavily fortified the Calais region because he believed Patton would lead the invasion there, which allowed the Allies to keep defenses fixed away from Normandy.
Juan Pujol Garcia known by his code name Garbo became one of the most trusted sources for German intelligence within the Double Cross System. He transmitted information confirming Allied deceptions even when it contradicted reality and claimed the Normandy landings were merely a diversion while the true attack awaited elsewhere.
Operation Bodyguard delayed the Fifteenth Army in the Pas-de-Calais for seven weeks after D-Day. Hitler refused to redeploy forces from Calais to defend Normandy for nearly two months despite evidence suggesting the threat was a feint.