In an ordinary orienteering event, competitors run a course which is marked on their map from the start, through a series of mandatory locations that must be visited in order, and then to the finish.
The start is drawn on the map with a triangle, the mandatory locations, or controls, are drawn as circles and are numbered in the order they must be visited, and the finish is drawn with a double circle. The start, controls, and the finish are connected with lines in the order they must be visited to help follow the course visually.
At the location of each control, there is a marker, called a control flag, which has a unique identification number or code. Competitors can check the code against a list given to them prior to starting to ensure it is the correct control.
Control flags usually have some type of device to record the competitors' visit. It may be a uniquely patterned hole-punch or, more commonly these days, an electronic device, which works with a memory stick carried by the competitor. This is how the race organisers ensure that competitors have completed the course successfuly.
Competitors choose their own route between each control. Simple routes involve following tracks and other line features like fences or creeks, more complex routes might involve following a compass bearing, running between point features like boulders or thickets, or following the contours. Finding the best route for you is the challenge.
At the finish, competitors hand in their control card or download the data from their memory stick to a computer. Results are then collated and if memory sticks (also called electronic punching) were used you can find out how long you took for each control and compare to other runners.