So a Theorist graph shows all this neat stuff. Where is it?

Well, it's in this space. For a 2d graph, it's in a 2 dimensional space, a flat area. For a 3d graph, it's in a 3 dimensional space, a spacious volume. To deal with these mathematically, we need a coordinate system.

If you open the details of a graph, you can see the limits of the graph. You can type in new numbers to change these limits. Or, you can click and drag to see the limits change. You can also use the knife or rocket, and see their effect on the limits.

The popup menus also control what you see, but in more subtle ways.