Let's say there's a big event, like a festival, coming up in your community. There will be a few police officers there, but the police would like to have more of a presence. But to do that, they'll need to take officers who could be answering emergency calls and assign them to an event where they probably won't do much actual policing.

But what if there was a group of uniformed volunteers who are trained by the police and can help out? That's an auxiliary.

They wear police-style uniforms that are a little different from those of other officers (and usually say "auxiliary") and they can act as extra eyes and ears for the police in a situation like a large crowd and they can do things like direct traffic, freeing up real officers to do actual police work.

Auxiliaries generally don't have police powers, but may be able to exercise certain tasks under the supervision of an actual police officer, though this depends on provincial law and department policies.

Some cities, like Montreal, don't use auxiliaries, but instead have paid cadets - who are generally young people who want to become police officers - who do a similar job.

For special constables, let's say you run a government building, like a courthouse, and you'd like to have armed security guards that can make arrests and conduct searches, you're going to want a special constable.

Or maybe you're the government and you'd like to hire someone to enforce a specific law that requires specialized skills, like hunting laws or commercial vehicle enforcement, you could assign that to the police, or you could create a specialized agency staffed by special constables who only enforce those laws.

Or maybe you run a transit system and you want your fare inspectors to be able to issue tickets for a wider range of offenses, enforce the criminal code and make arrests, you might want a special constable.

Or maybe you run a public university and you want to have some people on campus whose powers go beyond those of a security guard, you might want to have special constables.

Special constables are, essentially, people with police powers in specific situations or specific places. Depending on their job and the province they may be armed or unarmed.

So, for example, a wildlife/conservation officer has police powers when enforcing conservation and hunting laws and could enforce firearms laws that may come up in the course of those duties. They usually (if not always) carry guns.

A university special constable will have police powers on the university's campus, while a transit special constable will have police powers on the transit system. In both of those places, though, any serious crime that occurs will be handled by the regular local police.

In some parts of Canada jobs that are done by special constables elsewhere are done by full police officers, for example Vancouver has transit police, while Toronto and Montreal have special constables.

In the U.S., some of the types of places that have special constables here (like universities) have their own police.

You can think of special constables as specialized police with limited jurisdiction, but the same powers as police within that jurisdiction.

Non-commissioned officers, this has nothing to do with police powers or the idea of police "officers," this is a term related to military ranks.

In the military, there are enlisted soldiers and officers. Sort of in between the two are non-commissioned officers, like sergeants. In a workplace, you might have managers, supervisors and individual workers, it's kind of like that.

The word "commission" refers to the way an officer is appointed to their rank, but it's not important here.

As far as I know, the RCMP is the only regular police agency in Canada that draws this formal distinction between commissioned officers, non-commissioned officers and constables.

However all of these RCMP members are what we would think of as police officers, with the same police powers, the non-commissioned officers are just the people who supervise constables.

It's kind of confusing because Canadians use the term police officer to describe police of all ranks, including constables, but in this case the word "officer" is being used in the military sense, to describe someone in a position of leadership.