When opening an example magic file, how can I probe to see what layers it contains? Is there a way to select a layer and see what it is?

Type key "s" with the mouse pointer over a layer to select it (type "s" more times in the same place to select an entire net), and then type the command "what". Key "a" is an area selection, and "what" will return a list of all layers, labels, and cells in the area selection.