In grammar, the relationship between the action/state of the verb and the subject is expressed in two forms of voice: Active voice and Passive voice.
Active form: In active sentences the subject is doing the action, and the object is receiving it.
{Thing doing it i.e. subject} + {verb} + {thing on which it is done i.e. object.}
E.g. The professor teaches the students.
Passive form: In the passive form, the action is done by the object.
[Thing receiving action] + [be] + [past participle of verb] + [by] + [thing doing action]
E.g. The students are taught by the professor.