The fourth wall is a term used in film/theater production where the viewer sees the production as a “room” with 3 visible walls (think of any time you’re watching a show take place in a house/apartment). The fourth wall is where the viewer sits and is invisible to the viewer, but the characters in theory would expect it to be there and act like they’re in a real place. Breaking the fourth wall is when a character acknowledges either the audience or in some other way interacts directly with the viewer’s reality as opposed to staying constrained to their own universe.

So, for this meme, Anakin (1st panel) is acknowledging that he’s being filmed even though the character should have no idea they’re even in a piece of film.