Action Command
An Action Command (also known as a Timed Hit) allows a character to do significantly more damage to an enemy than a normal hit. Often, Action Commands occur when the player presses the "A" button right before the party member hits his opponent. Additionally, party members will receive less damage if the player presses "A" right before an enemy attacks. In Super Mario RPG: Legend of the Seven Stars, they were called Timed Hits, and are the key to success in the game. The Paper Mario series, and the Mario & Luigi series both use the term "Action Command".
In Paper Mario, Twink gives Mario the Lucky Star, a special pendant from Peach that allows the plumber to perform Action Commands. This artifact proves useful in the upcoming battle against a Magikoopa; a fight that occurs after Mario visits Shooting Star Summit for the first time.
In Paper Mario: The Thousand-Year Door, they reappear, and also have Stylish Move , which allows you to gather more points for your Star Energy. They are available from the start. While Action Commands are not used in Super Paper Mario, similar moves called Stylish Moves do appear.
In the Mario & Luigi series only, Mario and Luigi can entirely avoid getting hit by enemy attacks by using the action command. They can jump over their enemies or hit them with hammers to prevent them from attacking. Also in the Mario & Luigi series, the attack is performed worse when the action command is timed overly wrong. Mario & Luigi: Partners in Time also has a special action command involving the babies in piggy-back mode.