Hi Andrew,
Press the blue help button on the left/top map tab to get to the help page here
Which has a brief explanation of the layers.
Its worth following the links to the source data from the help and from the attribution at the bottom right of the map
e.g.
and
Hope that helps.
I have just today added LIDAR hill shading for England and Wales.
On the Geological maps and the Living England ground cover map, you can use a right click to look up their web feature service data for the point clicked.
Donations welcome !
Bill