In active voice, the subject does the action in the sentence.
In passive voice, the subject does no action. The subject is acted upon.
Both active voice and passive voice are used in writing, but active voice makes the writing more interesting.
Look at this writing sample. It is all written in passive voice.
Mary was driven to the store by Mom. Mary was met at the store by her friend Suzy. The store was entered by the two girls. Much time was spent at the store by Mary and Suzy. Several items were purchased by the two girls. Much fun was had by the two friends.
Notice what happens with writing in passive voice. Every sentence uses the word by.
The girls were driven by Mom. The store was entered by the two girls. The fun was had by the two friends. Did the story get boring once you realized that every sentence had this repetitive passive voice structure?
Now look at the same story in active voice:
Mom drove Mary to the store. Mary’s friend Suzy met her there. The two girls entered the store. They spent much time shopping. The two girls purchased several items. They had lots of fun.
You will probably agree that this story feels more alive; it has more action.
Do your best to write in active voice. Let your subjects perform the action in a sentence. When you do, your writing will be livelier and more fun to read.