Transformers vary in size and design, but in their basic form they consist of two coils of wire.
The coil directly linked to the power supply is the primary coil. The other, in which a current is induced, is termed the secondary coil.
Generally, the primary and secondary voltages should be equivalent (ignoring heat losses) if the number of turns in each coil is the same.
But if the secondary coil has fewer coils than the primary, it will take on less voltage. The main use of transformers is to channel electricity of high voltage to a circuit in which a lower voltage is needed.