Tomography is like taking an X-ray picture of something, but instead of just one picture, we take lots and lots of pictures from different angles. Then, we use a special computer program to put all those pictures together and make a 3D image of the thing we took pictures of.
Imagine you are playing with a big toy castle, and you can only see the front of it. But you want to see what it looks like from the side and the back too. So, you start walking around the castle, looking at it from different angles. Each time you move, you take a picture of what you see.
After you're finished taking lots of pictures, you can sit down and put them all together to create a 3D image of the castle. You can now see what the castle looks like from all sides, even though you only saw it from the front at first. Tomography is kind of like that, except we use X-rays or other kinds of waves to take pictures of things inside our bodies, like bones or organs. We can look at those pictures from different angles and use them to create 3D images of what's inside our bodies. This helps doctors to see if there are any problems or illnesses that need to be treated.