One of George Orwell’s rules of writing is
Never use the passive where you can use the active.
To apply this rule, of course, you have to know what he means by passive and active. It has to do with a feature of English verbs called voice.
A sentence is in the active voice when the doer of the action expressed by the verb is the subject of the sentence. Here is an example of a sentence in the active voice (the verb is in bold):
Donald Trump has put the lives of American Muslims in great danger.
Donald Trump, the doer of the action (has put) is the subject of the sentence—Donald Trump comes first.
Now look at a passive voice version of that sentence:
The lives of American Muslims have been put in danger.
In this sentence, the receiver (American Muslims) of the action (have been put) are the subjects. The doer of the action—Donald Trump—isn’t mentioned. If he were mentioned, it would have to be in a by phrase, i.e.:
The lives of American Muslims have been put in danger by Donald Trump.
The awkwardness of the passive voice with the by phrase is precisely what Orwell wanted to avoid.
If the doer of the action either doesn’t matter or isn’t known, the passive voice is preferred:
Donald Trump might be elected President.
We know who will elect him.
Several mosques were vandalized.
The fact that the mosques were vandalized is the focus of the sentence, not the knobs who vandalized them.
The passive voice is sometimes called the voice of tact because it can be used to mask the doer of a bad action:
Mistakes were made.
Note that a verb must be transitive, i.e. capable of taking an object, to have a passive voice. The following sentence can’t be made passive:
Donald Trump’s supporters couldn’t care less about Muslim lives.