Transformer to change the voltage value acting AC voltage into the appropriate usage. You can change has increased and decreased, usually to reduce the voltage to be used in electronic circuits.
Transformer will convert AC voltage to a voltage suitable for the application. You can change it up and down. Typically this will reduce the pressure to be used in electronic circuits.
As the transformer will also changed voltage alternating current into a voltage suitable for use as the change increase and decrease. This is usually the pressure for use in electronic circuit