The After Action Report is an evaluation of how a mission or goal was completed. This gives a summary of what happened during an mission to assess how well the operation went.
In the Splinter Cell series, this evaluation is mostly dependent on how well the player performed in regards to stealth. Starting with Splinter Cell: Chaos Theory, missions are graded on a percentage, with the level starting out at 100%, and deducts being added depending on non-stealth actions that the player performs. Actions that deduct the player's score could be sounding alarms, alerting guards, or even killing enemies may result in loss of 'mission rating'. This was carried over in Splinter Cell: Double Agent, with added difficulty: score would be deducting if the player killed enemies, and even when they knocked out enemies as well.
In Splinter Cell: Conviction, the player was never graded (although certain P.E.C. challenges would be unlocked, depending on if the player had met the conditions). In Splinter Cell: Blacklist, players were graded in playstyles instead of only stealth. Players would earn points more depending on the playstyle (such as Panther, Assault or Ghost) instead of being graded on stealth-based actions.