filling the frame
filling the frame is pretty self explanitory.
when photographing you take a picture of something that is appealing to your eyes, ou may stand back and admire and take a picture but filling the frame takes a little more work, easy work. you have to get up close to the main subject of the photogrpah and fill the frame with it and then later crop it inot a square. or if you are photogrpahing with something like your phone you can use the square setting on your camera and just zoom.
here are some examples.