This is called a third man run
because the runner is the third man in the play. The third man can sometimes
start the passing sequence, and sometimes he is on the blind side of the
play and not involved at all when the run starts.
Third man run - first
In the figure above, A2 starts with
the ball in a standard mid-field/attacking position. He exchanges passes
with A3. This draw D1 upfield, and D2 over to provide second defender cover.
D3 is also distracted by what’s
happening, and misses the blind side run by A1, who is making the third man
run in this case