A single action pistol (for example 1911A1 or Browning High Power) must be manually cocked in order for the first shot to be fired. A double action pistol is "self cocking" i.e. pulling the trigger cocks and fires the weapon.

Basically a single action firearm can only fire after being manually cocked, a double action uses the trigger pull to cock and fire. Really basic explaination

Not to beat it death. But I think of it as if the trigger cocks and release double action, if the trigger just relases than single action.

Gentleman,
Thanks for the info. Are there any advantages to either type of action? What would your recommendations be for an FNG to learn how to shoot on?

You absolutely postively need to take an approved NRA Basic Handgun/Safety course.

Most of your basic questions will be answered and you will be one step closer to obtaining a carry permit in most states.

The cost of the course is a lot cheaper than making a mistake in purchasing the wrong handgun for you.

There is usually less force needed to pull a trigger in SA.

I agree that a good handgun safety course would be a good idea. For a first handgun to learn to shoot with, I have always felt that a good double action revolver like a Smith & Wesson .38 K frame (model 10, for example) is a great choice. You can shoot it both single action and double action and once you master the double action trigger, you can learn to shoot pretty much anything after that.

Single action- the trigger does one thing releases the hammer.
Double action the trigger does two things cocks the hammer then releases the hammer.
I would recommend a good .357 revolver with 4" barrel. You will be able to practice with less expensive .38 spl. rounds to gain experience with but still have the option of full load .357 mag. rounds if you chose.

Single action means single action...the single action pulling the trigger performs is dropping the hammer or striker.

Double action means double action...the two actions pulling the trigger performs is cocking the hammer or striker, then dropping it.

SA trigger pulls are short and light; DA trigger pulls are long and heavy. Traditional DA/SA pistols can be decocked to put them in DA. When you rack the slide to chamber the first round, the hammer or striker is cocked. On a hammer-operated handgun, the hammer can be lowered (carefully) to put it in DA. Striker-operated handguns that can be decocked have decocking mechanisms as the cocking is done internally. If a pistol is DA/SA, once decocked it can be fired in DA mode. When the action cycles, the slide being forced back recocks the hammer or striker, and every subsequent shot will be in SA unless the shooter manually decocks it each time. DA trigger pulls sometimes act as a safety as they require a more deliberate effort to discharge the weapon.

Some handguns are DAO (double action only) or SAO (single action only). A SAO handgun can only be fired in SA. If it has a hammer or a decocking mechanism, it must be recocked in order to fire. A hammer-operated handgun requires the shooter to cock the hammer back, and a striker-operated handgun requires racking the slide back about halfway, which is enough to recock the striker, but not enough to eject a round from the chamber. A DAO pistol is automatically decocked after each shot so every trigger pull is DA.

Some prefer the SA pull but prefer a DA/SA so the first shot is in DA (hence the DA acting as a safety). Some prefer the consistency of DAO or SAO so each trigger pull is the same length/weight.

Some handguns such as Walthers P99s, S&W M&Ps, and Glocks are essentially half-cocked when in SA, and pulling the trigger finishes cocking them, then drops the striker. So basically they're in between a SA and DA. Glocks do not have decockers and are always half-cocked if a round is in the chamber. Walther P99s and S&W M&Ps have decocking mechanisms and can be fired in DA with the exception of the Walther QA (quick action) that must be recocked to half-cock to be fired. The decocking key on the Walther QA essentially renders the gun unable to fire unless it is recocked, similar to lowering the hammer on a SAO pistol (like a 1911). Hope this helps.

The S&W M&P does not have a decocker, and does not operate from a "DA" mode.

I know, I don't know why I wrote that. Sans the part about the M&P though, accurate info.