Passive voice

Study this example

Mary answers the test. ( Present tense)
The test is answered by Mary.

Mary answered the test. ( Past tense)
The test was answered by Mary.

The passive voice is a grammatical construction (specifically, a "voice"). The noun or noun phrase that would be the object of an active sentence (such as Our troops defeated the enemy) appears as the subject of a sentence or clause in the passive voice (e.g. The enemy was defeated by our troops).

There are many tutorials in you tube for the use of this voice or form of expression. Keep practicing.