Designated Hitter
A hitter bats for the pitcher and does not play the field.
How it actually works. The American League adopted it in 1973 and the National League resisted for forty-nine years. A club may also let a two-way player hit and pitch without giving the spot up, a rule written for Shohei Ohtani.
Why it is done, and when it is wrong. The argument was never really about offense. It was about whether a manager should have to decide between leaving a good pitcher in and hitting for him, which was the most interesting recurring decision in the National League game and is gone.
Batter's Eye: look up anything in baseball