Using the active voice is often cited as a guide for clear writing, but what does it mean? It means put the subject first in the sentence such as “Volunteers sold tickets”.
The opposite of active voice is passive voice or construction such as “Tickets were sold by volunteers”.
Active voice or construction is usually preferred because it is shorter, clearer and more direct. But not every sentence has to be written in active voice. You may want to emphasise the object by putting it first in the sentence such as “Tickets will be sold by volunteers at the door”.
Using the active voice rather than the passive is a key principle of plain English writing.