Normals are just basically "invisible" vectors showing which way the face is looking at. You can see them by turning on Display -> Polygon Components -> Normals (or something). Only thing you are interested in this case to do with them is to flip them to the other side if needed with Edit Polygons -> Normals -> Reverse.

*edit*
If you turn on backface culling you're gonna see only the "normal" sides of the faces...