(from the article `baseball`) When an offensive player reaches base, a pitcher must change tactics in order to prevent the runner from scoring. The pitcher will alter his stance ... Found on http://www.britannica.com/eb/a-z/w/42
The windup consists of the pitcher standing directly on the mound or right in front of the mound with both feet facing home plate. Pitchers throwing from the windup have the option of stepping behind the mound with their front throwing foot, before ultimately bringing it forward to home plate. Found on https://coachingkidz.com/baseball-terminology-the-ultimate-guide-to-terms-u
The windup involves a longer motion than the stretch. It has a big leg kick that is thought to give the pitch more power. The windup is used when there are no runners on base or there is only a runner on third. Found on https://www.baseballmonkey.com/learn/baseball-terms-slang-defined