I was reading on here about passive voice but didn't really know what active voice was. I read some examples but was hoping for more insight. What does it mean to write with the active voice?
When you write in active voice, it means that you're using a standard [subject] [verb] [object] sentence.
When you use the passive voice, it means that you reverse the subject and the object from the active form.
The meaning of the sentence is the same: Jack is doing some killing. Yet Jack is not the subject and killing is not the main verb. The sentence emphasizes all the wrong parts of itself by being put in this order. It uses more words and the picture it gives isn't as clear. When an action is performed, make sure you use that word as the action verb, and you will do just fine.
A verb is in the active voice if the agent of the verb (i.e., the pronoun/noun phrase that does the verb) is in the subject position (usually, but not always before the verb); it is in passive voice if the agent is in object position. Not all verbs are in either the active or the passive voice.
Geoffrey Pullum has three examples of sentences wrongly characterised in Strunk&White as passive in his 50 years of stupid grammar advice anniversary polemic, the first of which is:
Here there are two verbs, the first of which has no agent (it is a modal verb), the second of which is a participle, with its agent in subject position.
Not all verbs are in either the active or passive voice:
How to choose
The active voice has a built-in advantage that it is almost always simpler and briefer, because you don't need an auxiliary verb, which passive constructions need in English. So use the active unless there is a compelling reason not to.
The two most important reasons why the passive might be appropriate are, first, it can give finer control over information conveyed (e.g., Mary was killed!) or secondly, it can change emphasis by giving control over the order in which information is presented (e.g., It was Mary who Jack killed.)
An active sentence means that the subject is the one performing the action, that he is the one being active in the sentence. A passive sentence is a sentence where the action is being performed onto the subject, who is passively enduring the action being done upon it. If you have a sentence for which you can not tell if it is passive or active, just ask yourself if the subject's the one doing the action or is the action being done to the subject.
Since this is a site for writers, I assume you are more interested in the practical use of the passive and active voices than it's grammatical explanation. A lot of people will tell you that using passive voice is bad. Here, I must stand in defence of the passive voice. Using passive voice is not by definition bad. Passive has its uses and its purpose. It is like saying antibiotics are bad. Sure, if you use antibiotics for every little soar throat, you're not doing yourself any favours, but in certain conditions, they are the only thing that can help you. The same goes for passive voice. The trick is to know when to use it.
Here is the example where a passive voice is considered "weak":
Firstly, my apologies to the women in the example. If you look at the sentences, you will notice that they're not exactly bursting with action. Yes, horrible things are happening, but it doesn't feel energetic. That's because all the action is being done to a passive subject. If we change it to:
This example is much more energetic. It's because the subject is actively participating in the action. It is causing it to happen. This is where the scene profits from the use of active voice, and this is the reason they say passive is "bad". If you need a dynamic, active scene, use active voice when ever you can.
But this does not mean passive really is bad. Passive has its uses. The obvious ones being when we don't know or care who is doing the action, or it's implied:
It is usually implied who builds cathedrals - builders commissioned by the Church. Or we simply don't care, we are interested in the cathedral and when it was built, not in those who built it.
The less obvious, more subtle uses of passive are when you don't want the action to be dynamic. Perhaps you want to create a feeling of inaction, of subject's helplessness or unwillingness to take the action.
Sure, They carried him off to his room is more dynamic, more active, but it's not what we want here. We want to show the subject's inability to perform the action, to emphasize his passiveness.
The sentence "The city was ransacked, the men slaughtered and women raped or sold to slavery." implies a certain helplessness of the city and it's people to defend themselves from the fate that has befallen them. Maybe that's more important to us in that moment than the action. It can also depend on whose side we are, the winning side or the loosing side. So, the passive has it's uses. A skilled writer knows when to turn a "weakness" into an advantage.
In answer to Charles Stewart: I would suggest that any verb with a subject must be active or passive. Those are the only constructions we have. We can make passive versions of all your examples, so they must by definition be active voice.
@Jonny - The easy answer to your question is that a verb is active if it is in a normal tense form and is not in a passive construction, which involves different forms of the verb 'to be' + the past participle of the main verb.
He writes books / was writing a book / will have written a book - active This book was written a long time ago/ is being written right now/ had been written in Latin first - passive
Scientists and academics often use--rightly--the passive voice to shift focus from the actor to what is being acted upon. For example, "dry ice was dropped into the at and the ensuing results recorded." The actor is unimportant, so passive voice is acceptable.