At the peak of the stack we see the pictures. This is a film optimistic, which is clear with the exception of the image to be printed which is thick. (black) There are other methods, like painting straight onto the silk with a "hold-out" solution, but for this class we're using a film, or vellum printed on a computer.
After that, a photo-sensitive material called "photo mask" or "photo stencil", which behaves much like photo film, is exposed to strapping light using the film positive as a mask. In this procedure the light-exposed areas of the photo-sensitive "gel" emulsion becomes hard-bitten. The liquid areas of the stencil which are protected by the dense areas of the film remain unexposed and thus soft. In the "growth" stage of the method, the showing areas of the pattern remain hard-bitten, while the unexposed areas of the pattern soften and wash away, forming the image areas where the inks will pass through.
The "photo stencil" is embedded (either before or after exposure) into fabric prolonged very tightly across the printing frame. After the model dries, the "Screen Frame" is pressed against the substrate (a shirt in this scenario) and ink poured onto the plane of screen is dragged across the design using a squeegee. The results are ink deposited on the shirt.