From September 1 to 3, the app can be used for a "pop-up AR treasure hunt," according to Disney. At 20,000 retail stores around the world, the app will use your phone's camera to find a hidden AR icon. Scan the icon and a new character from the upcoming film "The Last Jedi" will be revealed.
Force Friday is the Sept. 1 quasi-holiday that celebrates all things Star Wars. Just don't confuse Force Friday with Star Wars Day, which is on May 4. (Because "May the 4th be with you" is too good a pun to ignore.)
Note that you need the latest version of the free Star Wars app, so look for version 2.3 or higher.