I have RPG maker 2003 I need to know those switches. Also how do you get the characters to move. By character I ment the one you are controlling.The basic switch event, which will allow you to be able to learn how to use them in more complicated situations once you master how to do this, is a treasure box. The purpose for the switch is so that the box cannot be opened and the item found over, and over, and over again.
Therefore, set a graphic for a closed treasure box. Place a text - such as "Found Potion!" Then place the command Add Item: Potion 1. Also, you may want to play the "Open" sound somewhere in there. Then, name a switch (one that has not already been used) to be turned on. Create a new page on this event, and set the graphic to an open treasure box. Set as the condition for this page on the event to be activated is that the previously mentioned switch is turned on. Place no commands in this box, as it is just an empty treasure box. This precondition can also be used to keep certain events from occurring until they are supposed to...but don't try to get that complicated until you have mastered the treasure box.
Hope that isn't too confusing, but you just have to play around with the commands and work with them. It can be difficult to learn at first, but once you get the hang of it you can get into more complicated uses of switches without as much hassle...but you just have to get through that somewhat frustrating learning phase. Good luck!