What is it?
the 12 bar blues is a very simple way to sort of frame-in a blues song. For beginners, it is a simple thing to learn that can be a great starting point and a great place to expand.
Let's start with the basics, it's called 12 bar because there are 12 measures, or bars, in the progression. The whole progression uses a 4/4 time signature, which means there are four beats in each bar.
What does it sound like?
When you are playing, or listening, to the 12 bar blues, count it off like this in your head:
one-and-two-and-three-and-four
That would be one measure, in the 12 of the progression.
Still lost?
Watch this video if you're feeling lost.
Once you get the simple pattern down, you can move it around the fretboard so it doesn't get repepitive. By the way, did you recognize the instructor of that video?