Use with Arduino

There are two common types of transistors: bipolar and field-effect.

                                  bipolar transistors

The picture shows the symbol bipolar transistor (left) and an illustration of a universal transistor (right). There are two types of transistors: NPN and PNP (depending on the type of semiconductor material). Its terminals are: B - Base C - Collector E - Emitor

                                      MOS transistors

The base will be used to control the transistor. Initially, this will not stream (between C and E). If the voltage base - emitter opening exceeds a threshold (about 0.65 V), it will absorb the current through the base and it will let through (almost) freely between C and E.
The image shows the symbols equivalent field effect transistor (FET - Field Effect Transistor). They work in the same way with one exception: they do not absorb energy when they are constantly open (as opposed to bipolar transistor). Switches faster, but their disadvantage is the fact that the command requires a higher voltage applied to the gate (Gate) - 1.8 ~ 10V