The minimap displays important battle information, such as the location of units, Victory Locations, and the general terrain. Your own units are shown as blue dots, and the ones currently selected as white dots. The red dots represent the enemy.
The Victory Locations are displayed as icons, and the colour of their outlines shows who their current owner is. Left-clicking on the minimap will move the camera to that location on the battlefield, and right-clicking will send the currently selected units there.