Voice

Voice shows whether the subject of the verb acts or is acted upon. There are two voices viz. Active Voice and Passive Voice.

Active Voice: A verb is called in ‘Active Voice’ when its subject acts.

e.g. Rama helps Mohan.

Passive Voice: A verb is called in ‘Passive Voice’ when its subject does not act but remain passive and is acted upon.

e.g. Mohan is helped by Rama.

Some more examples:
Active Voice
Suresh loves Sohan.
The builder is building the house.
The servant opened the room.
Some boys were helping the injured man.
I will finish the work shortly.
Why did write such a letter?
The boss told him that.
I am doing it.
Shall I do it?

Passive Voice
Sohan is loved by Suresh.
The house is being built by the builder.
The room was opened by the servant.
The injured man was being helped by the boys.
The work will be finished by me shortly.
Why was such a letter written by you?
He was told that by the boss. or That was told him by the boss.
It is being done by me.
Shall it be done by me?