Hey Matthew, glad you're learning a lot! The weird shading is letting you know that you have faces that are pointing in opposite directions. You can turn on Backface Culling in the viewport properties to see what it would look like in other applications like Unity. To fix this, select everything and recalculate the normals with Ctrl+N so that they're all facing outwards.
In blender 2.8 there is a "Show Overlays" menu that, while in edit mode, will allow you to actually see which way the individual face normals are pointing. I found it quite helpful when trying to troubleshoot one of my models that I was having a hard time subdividing in one of the previous tuts (and I couldn't tell that my normals were facing the wrong direction)