There will be a small blue ball on your map – that is your current position. It will move as you phone/device moves.
While riding you can use two fingers and pinches to zoom in or out on your device.
The Directional pointer at the bottom left of the screen can be in 3 different states:
Cursor at current position and map facing North
Cursor at current position and map facing in direction of travel.
Cursor not at current position
If you are looking ahead on the map and zooming in and out, often the cursor will move off of the current position. At any time, you can move back to showing your current position by touching this icon.
Here is a video that shows what some of the colors mean on The Next Trail. By the way, you can change these colors under Preferences (upper left corner on the app, three bars ).