Our model railways generally use electricity to create movement in a number of ways. There is direct connection to the track, the wheels and then the motor in the loco, or by use of radio control.
Direct connection to the track uses two different technologies. The oldest is DC (Direct Current) where a voltage is applied to the track when a loco is required to move. Zero volts leaves the loco stationary and as the voltage is increased to a maximum voltage (normally 12 volts, but could be 24 volts) the loco's speed increases.
The second method uses DCC (Digital Command Control). The controller generates an alternating voltage, usually 16 volts AC, which is present on all the track all the time. A tiny computer chip in each loco looks for a high frequency command signal on top of the AC voltage to instruct the loco. These commands tell the loco to move, or sound a whistle, or change direction for example. The same types of commands can also be used to tell a point motor to move, or a signal to be activated.