terminology - What exactly A flap is in the context of a cardboard box?

per this answer

The bits at the top and the bottom that tuck in to seal the box are called the flaps.

are there 4 flaps in the image shown below?

or the whole top is A flap?

Are these 4 parts also flaps?

My concern is if only the part that could be tucked in called flap, because I had got this answer (exactly the same one at the beginning of this post) originally.

The bits at the top and the bottom that tuck in to seal the box are called the flaps.