Yes. There are some other differences, but that's the main one. It must be cocked for every shot.
Another difference is the way the cylinder is loaded. Instead of releasing the cylinder and sliding it out to the left, there is a loading gate on the right hand side that flips out and you load one round, rotate the cylinder, load another, rotate etc.
Ejecting spent brass is different as well. The ejector rod that you have on your Ruger ejects all six cases at once and is contained in the center of the cylinder. It stays in the cylinder when you release it.
The ejector rod on a SA stays in the frame off to the right side of the barrel. It is pressed just like the other type, but it only goes into one chamber and ejects one case. The cylinder is then rotated a bit to the next chamber and the procedure is repeated until the cylinder is empty.
The design of the grip, sometimes called a spade grip is made that way so the revolver will "roll" upward to absorb and manage recoil.
I'll try and find something online that can explain it better than I can.
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It's mostly a matter of timing and location, that is, if it was made before 1900 and was widely used in the American West, then it's a "cowboy revolver". The majority of them are single action, and most of the double action ones strongly resemble the older single actions. The National Congress of Old West Shootists (NCOWS) has a list of approved revolvers that are selected for their close resemblance to what we're talking about here. You'll find the list at NCOWS Approved List.