For the FREE (TT STD) maps there is no map key (legend) as it uses the default icons, etc. for all generic OSM maps for Garmin devices.
For the TT HD Topo, TT HD Topo Pro and 1:50K Look n Feel maps a map key/legend is supplied with the map (as a PDF file), this included all electronic, automatic and card options.
The TT HD Topo, TT HD Topo Pro and the TT 1:50K Look n Feel maps also use a similar iconography to OS Landranger maps (for rights of way), so footpaths are red and white dotted lines, bridleways are red and white dashed lines, and cycleways are blue and white dashed lines, etc.
However, you can find what the item is on any of our maps by simply moving the pointer to it, and the Garmin device will tell you what is represents (on Fenix and related models, you may need to push the top righthand button once the item is highlighted (in the cross hairs).
On Fenix and related models, you may need to long push the top right-hand button once the item is highlighted (in the cross hairs) when using the Pan/Zoom functions.