There are many different kinds of DIP switches. Some of the most common are the slide, rocker, piano (side), and rotary types.
Rotary DIP switches contain multiple electrical contacts, one of which is selected by rotating the switch to align it with a number printed on the package. These may be large like thumbwheels, or so small that a screwdriver must be used to change them (although there are also small potentiometers of this type).
The slide and rocker types, which are very common, are arrays of simple single pole, single throw (SPST) contacts, which can be either on or off. This allows each switch to select a one-bit binary value. The values of all switches in the package can also be interpreted as one number. For example, seven switches offer 128 (27) combinations, allowing them to select a standard ASCII character. Eight switches offer 256 (28) combinations, which is equivalent to one byte.
The DIP switch package also has socket pins or mounting leads to provide an electrical path from the switch contacts to the circuit board. Although circuits can use the electrical contacts directly, it is more common to convert them into high and low signals. In this case, the circuit board also needs interface circuitry for the DIP switch, consisting of a series of pull-up or pull-down resistors, a buffer, decode logic, and other components. Typically, the device's firmware reads the DIP switches when the device is powered on.
With the popularization of surface-mount technology, these switches are now commonly available in non-DIP surface-mount package types. They are, however, still referred to as "DIP switches", as the term has become associated with the style of switch.