The student council approved new dress code rules.
A sentence is in active voice when the subject performs the action denoted by the verb, that is to say, the sentence directly tells what a person or thing does. It follows the following sentence structure: subject + verb + object.
The student council (subject) approved (verb) new dress code rules. (object).
In a passive voice sentence, the subject is not that important or relevant and the object becomes the main focus.