(EDIT) The "ASCII art" I did didn't look as good after posting it, but it was like a "cross", imagine a square screen but missing 4 little squares at the corners.
Not entirely correct but you can get the idea. For the theatrical version, the widescream frame was chosen, cutting off the top and bottom, but just a little. For the TV, they get the 1:1.33 section, the middle one, and cut off the sides, but just a little bit.