S.P.E.C.I.A.L. stands for:
In Fallout 2 the SPECIAL stats are chosen during the character creation process. The player chooses its stats and tag skills on one screen.
In Fallout 3, the SPECIAL stats are not chosen until the player has moved around in the game. In previous Fallout games you would select your SPECIAL and tag skills before playing the game, but in Fallout 3 the player is able to move around as a baby before opening a SPECIAL book allowing the player to chose its SPECIAL stats. The tag skills are not chosen during this, the tag skills are selected for the player as he makes a career test in the vault. The outcome are just suggestions, calculated by the answers the player gives on the test. The suggested skills are still editable after the test, and the player is also able to skip the test and fill in the stats without having to take the test.