"Dimetric projection" is a way to draw a 3D object on a flat piece of paper so that it looks like it's popping out of the page.
Imagine you have a toy car that you want to draw on a piece of paper. If you drew it normally, it would look like a flat picture of a car. But with dimetric projection, you can draw it so that it looks like you're looking at it from an angle.
Think of it like looking at the toy car from one corner of a room. That makes the car look like it's turned slightly to the side. In dimetric projection, you draw the car so that it looks like it's turned a bit to the side, just like you would see it from that corner.
This way of drawing things makes them look more realistic and helps you see all the different parts of the object, like the wheels and the windshield, as well as how they relate to each other in a 3D space.