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http://www.staredit.net/index.php?tutorial=116Switches are a way of recording information for later use.
They don't do anything at all by themselves, and they're only affected when a trigger runs the action 'Set Switch'.
You can check the state of a switch (whether it is 'set' or 'cleared') using the condition 'Switch'.
Each switch must be either 'set' or 'cleared', and all switches start 'cleared' at the start of each game.
For example, you might have a map where a person needs a key to get access to an area. When they find the key, you can record that information by setting a switch. When they reach the door, you would check to see if they had the key or not by using a condition such as "'Switch 1' is set".
This is useful, because the initial condition for finding the key (probably something similar to "Player 1 brings at least 1 men to 'key'") would no longer be true, and we wouldn't be able to check it without something like a switch.