Andy did answer your question, I suggest you go to the website he provided and actually read the SDL documentation. The SDL docs are very good and spell out everything you need to know.

pSurface is simply a pointer to an SDL_Surface.

RTFM is a suggestion to read the manual. The implication is that either your problem is one that can be readily addressed by reading standard documentation on the subject, or that your question does not accurately represent your problem.

Also, having crude or offensive sigs or location information probably doesn''t help encourage anyone to respond with even the information requested, never mind providing additional information or explanation beyond a terse redirection to a technically valid reference.

SDL_FillRect() draws a colored box or >fills a rectangle< with a color..