Pitching from the stretch.
Pitchers throw from the stretch position when there are runners on base. They turn parallel to the pitching rubber so they can face the base runner as a left handed pitcher, or turn to third base as a right-handed pitcher, with their back to the base runner. In this case, they can throw over, over to first base to catch a runner napping, or to keep him at bay from stealing as they deliver a pitch.
It's imperative that pitchers vary their looks and are not consistent, but rather are consistently inconsistent in their pick off moves and looks to first base. Some pitchers employ a slide step, so as to deliver the pitch quickly, and that the batter is thrown off, as is the base runner, so we cannot get a good jump and steal second base. Effective pitchers at the higher levels, who are relief pitchers, must do a good job of pitching from the stretch position.
These are some examples and tips of pitching from the stretch position.