A flash is a bright light that you only see for a very, very short time. When you take a photo with a camera in dim light you usually use a flash to light the objects in the photo up so you will be able to see them.
A flash can also be used to describe something you only see for a very short time, or didn't quite see clearly, as in "I saw the rabbit flash by".
You flip something when you quickly turn it over, either half-way over so it is upside down or flipped over all the way so it comes back to where it was to start with. The boy in the picture is doing a backflip.
Flitting means to move quickly from one place to another, the way a small bird flits between branches.
Fis forFly (motion)
Flying is a way of moving through the air. Most things that fly do it because they have wings, but helicopters fly by using a rotor.
You forget something if you don't do it, but not on purpose. You might forget to do your homework, or go out and forget your keys.
The man in the picture has forgotten to put his pants on before he goes to work.
