If you hover the pointer over them, a tip bubble should tell you.

So I can only use a mouse to do that ? Not a function available on a tablet?

Depends on your tablet. On some, a long press will result in the icon title being displayed at the top of a menu. It's not really in the website's control if the browser doesn't do anything useful with the information it is sent.

mjray is spot on (as ever) - those are the symbols. Ultimately there'll be a cycle.travel app specifically designed for phones/tablets, including offline mapping, rather than shoehorning the desktop web interface into it. Just need to find the hours to finish it. :)