A pinhole camera is a type of camera that you can create yourself using everyday materials like a cardboard box, tape and aluminum foil. Imagine the camera as a dark box with a tiny hole in one side.
When you take a picture with a pinhole camera, you need to point the tiny hole (the pinhole) towards the thing you want to take a picture of. The light from that thing will go through the hole and create an upside-down image of it inside the box, on the opposite side of the pinhole.
You can see the image by putting a piece of photo paper or some other light-sensitive material inside the box where the image is being formed. After you let it sit for a while, the light will make an impression onto the paper and create the picture!
It may sound complicated, but it's actually a really simple and fun way to take pictures with a camera that you made yourself!