Actually, if you were to get yourself a picture book----something on the order of The Standard Catalog of Smith & Wesson, you wouldn't be wasting your time asking questions like this.
On the other hand, the current edition (4th) is obsolete, so wait for the 5th edition. It'll be along in July---or at least it's supposed to be. Most everything that was not quite right in the 4th will be fixed, and anything worth talking about since it came along, 2016 or so, will be in there--even almost certainly including such lingo as "pre" this or that; never mind S&W never made anything called a "pre" whatever.
Or maybe not---hope springs eternal!
Ralph Tremaine