@freiredesign
If you are talking about the back wall it looks like you have multiple “planes” in the same y depth. Planes that all share the same y coordinate all tend to interfere with one another. You could bring them in a little from the wall and that should fix it.
But if it is a different thing you are talking about perhaps you are referring to the backface culling
Or! If you are using @jlampel provided room from the fundamentals of modeling course then he set up the scene to enable backface culling (the camera only cares about faces that have the normal pointing outwards and ignores the other side so it appears “see through”). This is not a problem but you can turn off back-face culling (i believe it is in the header but I don’t have blender nearby)
Or! There may also be a problem with some faces that have normals flipped on some faces but not on others. You can hit A to select all daces in edit more and then Shift + N to flip all normals to match.
