The only big difference between the American League and the National League is that the AL uses the "Designated Hitter" (or DH). The Designated Hitter is a player who does not play in the field, but is used to bat for the worst hitter in his team's "lineup" (usually the pitcher). The NL does not use the Designated Hitter, and all players in the "lineup" must bat and field for themselves. If the DH plays an NL game in an NL park, he often plays First Base if at all. If they play in an AL park, the NL can use a DH.