Dumb question, but I don't know what these two terms mean. Any help appreciated.
Thank you,
Bill

In single action, the hammer is cocked, & you only have to pull the trigger a hair to fire the round. In double action, the hammer is down, so you have to pull the trigger a long way which pulls the hammer back, & then fires the round. Since the hammer is being cocked in double action, you have to pull the trigger harder than single action. GARY

Not a dumb question. It's better to ask and gain the knowledge than pretend to know and not. I run into a lot of the later when I talk to people about guns.
Not here of course
I hear blatantly incorrect info a lot in stores though, usually from sales people.

No, not a dumb question at all! This is how we learn.

Once in awhile you will also see TDA and DAO. TDA is "traditional double action" where you can pull the trigger when hammer is down OR you can manually cock the hammer and fire in single action. DAO is "double action only" which means the gun cannot be manually cocked and fired, it can only be fired by pulling the trigger. Lots of law enforcement officers (LEOs) like DAO as the gun fires exactly the same way every time the trigger is pulled with no single action option.

Hang around the forum for awhile and I promise you will learn a lot.

__________________
I'm gonna grow fins.

Single action/double action applies to pistols, too.

The ubiquitous 1911 is single action. It is most frequently cocked by racking the slide, not thumbing the hammer.

There are a lot of DA/SA pistols out there. First shot is DA (trigger pull cocks and drops the hammer), and the cycling of the action leaves the hammer cocked, so subsequent shots are SA. Big drawback is trigger feel is very different between first and other shots.