A camera obscura is a camera-less camera you look through the tube and there is tracing paper at the other end and when you look through the tube the photo at the end will be upside down.
This is how you make it:
1st you will get your equipment
2nd you will get your tube and put tracing paper at one of the end and stick it down
3rd you will get a smaller tube and stick it on top of the tube where you put the tracing paper and stick it down with duck tape
4th then on top of the small tube you will put tin foil on top of it and stick it down
5th you get a pin and put a really small hole in the tin foil