WP Distance
Waypoint panel indicates 4 things. Waypoint direction, waypoint number, waypoint distance, and crosstrack error.
This panel is hidden till there is an active WP!
Waypoint direction indicates the direction to the next waypoint, relative to your plane.
You need a magnetometer to make this panel work more precisely.
It still works well with only GPS, but when there is strong wind, than it can show a bit different waypoint direction (usually it is a good approximation).
Waypoint number is the number of the waypoint that the plane follows at the moment. It is the same number you define in MP.
Waypoint distance indicates your plane distance from the next waypoint, in meters if you set metric system for units of measurement, and feet if imperial.
Crosstrack error telss you that how far your plane is from the defined vector. (Think of it like it is a car, should travel on the road, and if crosstrack telss you that you ar 11m off, that means you are driving 11m next to the road where you suposed to be.)