Pointers to Structs?

Hey guys, I'm having some trouble with pointers in C++

Lets say we are setting up an SDL surface

SDL_Surface *screen;

Why do we make it a pointer? I looked in the header file for SDL_Video and SDL_Surface is a struct! So that means we are pointing to a struct, but then how are we able to do this?

screen = SDL_SetVideoMode(...);

So yeah my question is basically, how does pointing to a struct work?

>>1
It would be the same as saying

struct *screen { /* Contents of SDL_Surface */ };