Photograms are created without a camera or negatives but by directly exposing photographic paper to light. Objects can be placed at some point between the paper and the light source to act as "negatives" by casting shadows on the page.
For my photograms, I played with motion and change in focus in my light source and used fabrics, meshes and even other photograms as the light moduating objects. It is a lot looser and more spontaneous than traditional darkroom phototgraphy and needless to say, it is fun.