With these sliders you can set the latitude and longitude for both your departure and arrival location on Earth.
Here you can choose what kind of map will be displayed. You can also choose wether or not to display geodetics, loxodromes or the grid given by parallels and meridians.
The map area: in yellow you can see the geodetic path between your selected points i.e. the shortest path between them; in light blue the minimal rhumb line (also called loxodrome) i.e. the shortest path between the chosen points that intersects every meridian with the same angle, thus avoiding bearing.
You can also draw with your mouse and see the correspondant path on Earth.
The globe area: you can drag the globe with your mouse in order to look at the path you have selected. At start, both geodetic path and rhumb line are already drawn.