The easiest voice to identify is passive voice, which is the one you want to avoid most of the time.
The verb ‘be’ is an irregular verb and has EIGHT different forms. No one knows and no one really cares, and the reasons aren’t important right now.
In particular, voice affects the relationship between the action or the state that the verb expresses and the subjects or objects of that verb.
If the subject of the sentence is the doer of the action, the verb is said to be in the active voice.
(It might also be said that it's the normal voice when speaking in English.) It leaves no ambiguity as to who the subject of the sentence is, and what that subject is doing.
However, while the use of the active voice – against the use of the passive voice – is typically counseled in high school as a rule, there will be times that the passive voice is needed.
In the first instance, knowing that a cure has been discovered is far more important to the reader than knowing who made the discovery.
Passive voice is often used in scientific reports where the results of the experiments are the focus of attention and not the person who performed them.
Active voice is the secret you really want to know about, because if you don’t then you’re going to be left out of the loop in a big way.
And it’s for this reason that you need to be able to tell them apart.