Besides the simple type of switches that are only either open or closed (on or off) there are also many other configurations that that allow a switch to select one of several circuits depending on its position.
The simplest type of switch is the single pole single throw (SPDT). The SPDT switch has two terminals that are either connected or disconnected. Another type of switch is the single pole double throw (SPDT). SPDT switches can select one of two connections to turn on. Many times these switches will be labeled with the abbreviations NC, NO, and COM; these stand for normally open (NO), normally closed (NC) and common (COM). These are the normal connections that are the default state of the switch.