Graphs are a view onto a space, either an area or a volume. By clicking on different parts of a graph, you can move around and see what you want to see.
In Theorist, we make a distinction between the actual data to be shown (in red, in this graph), and annotations such as the purple grid lines and axis labels. When you slide around, for instance, you slide the data, but the annotations stay in place, continuously showing you what location corresponds to what x and y coordinates. You cannot zoom in, for instance, to one of the numerical axis labels. Why would you want to? That's not the data.