It is the name given to a device used to produce images on a sunny day or when there's a lot of light. To create this device, you would need a box or room with a hole in one side. When the light goes through the hole, it projects the external scene and then appears on the inside of the box or room upside down
In class we were able to try camera obscura in our art classroom. We had we had put black card and tape on all the windows and doors, covering any light. We then made one hole in the card that was on the window so only a little bit of light would beam through the classroom. But disappointingly the weather was not willing to compromise , so there was not enough light to complete the experiment.