A turnaround is a two bar phrase which can be found at the end of each verse in the vast majority of Blues songs. Turnarounds usually begin on chord I in bar eleven of a 12 bar progression and move to chord V in bar twelve. A turnaround has the effect of finishing a verse while setting the progression up for the start of the next verse. Here is an example of a turnaround. first by itself an then at the end of a 12 bar progression.
This is a variation on the previous turnaround. Instead of playing two notes together, the same notes are played consecutively, alternating between the third and fourth strings.
Now listen to the effect when the turnaround is added to a 12 bar Blues progression.