Admittedly, this was something even I was confused about early on. For a while, I was incorrectly referring to 12-fret guitars as "short scale" guitars, assuming they were one-in-the-same.
In fact, a guitar's scale length and its number of frets are mutually exclusive. (Just because a guitar only has 12 frets, doesn't mean it's a short scale, and vice-versa.)
What is a 12-fret guitar?
We'll start with the easiest questions first. When a guitar's "fret number" is called out, it refers to the number of frets from the nut to the top of the body.
Most standard guitars these days have 14 frets from the nut to the body. Classical or compact guitars often have 12.
|14-Fret Yamaha vs 12-Fret Recording King|
What is scale length?
The scale length of a guitar is the distance measured from the nut to the bridge. (The scale length on my Yamaha fg700s dreadnought for example, is 25 9/16".)
Here is a comparison of a 14-fret fg700s next to the 12-fret Recording King RPH-05 parlor. Notice that even though the RPH-05 is much smaller, their scale lengths are relatively equal, due to the positioning of the bridge:
Scale length is another way guitar manufacturers can control the guitar's size. The shorter the scale length, the closer the frets are to each other. There are advantages and disadvantages to each--shorter scales might be better for holding chords, longer scales might be preferred for finger picking as an example.
Okay, so what is a "short scale" guitar?
This is where it gets tricky, because there is no standard definition of a "short scale". Different manufacturers have different interpretations of what they consider "short". Furthermore, this may vary by model and may even change with models over time.
The term "short scale" by itself then, really doesn't say much as to what the guitar may or may not look like, and isn't as useful as knowing the measurement of the scale length.
As a rough rule of thumb, I would probably consider anything under 25.4" a short scale (certainly anything under 25"). But again, it really depends on who you're talking to. (For a more in depth look at scale lengths, check out this in-depth article on guitarnoise.com.)