Okay kiddo, so you know how sometimes you see shapes in the stars at night? Like maybe you see a big dipper or a little dipper, or maybe you pretend that some stars make a picture of a bunny or a dragon? Well, some grown-up scientists a long time ago decided that they wanted to organize all these different shapes that people saw in the stars, so they made something called constellations.
Now, a long time ago these scientists only knew about a few of the constellations, but as time went on people started exploring space more and more, and they found more and more shapes in the stars. So these scientists had to keep adding new constellations to their lists, until they had a total of 88 modern constellations.
Now, these 88 constellations aren't all the same size - some are bigger and some are smaller. So when we talk about them by area, we mean how much of the sky they cover. Each constellation is like a puzzle piece that fits into a big picture of the night sky.
So to sum it up kiddo, the 88 modern constellations are different shapes that people saw in the stars, organized by grown-up scientists a long time ago. Some are bigger and some are smaller, and they fit together like a puzzle to make up the big picture of the night sky.