This time signature is called the twelve eight time signature. It tells you there are twelve eighth note beats in each bar.
A bar of eighth notes in twelve eight time sounds the same as a bar of triplets in four four time. Although there are twelve individual beats which can be counted, twelve eight time is usually still counted in four as demonstrated in the following example.
The beats can also be subdivided into sixteenth notes as shown here. Be careful with the counting.
Here is a Blues lick in + time which makes use of sixteenth notes.
It is also possible to swing 16th notes as shown in the following lick.