Some more important info about special abilities:
Dribbling
The player, when COM controlled, favors dribbling.
Tactical dribble
The player, when COM controlled, favors dribbling in order to keep possession.
Positioning
Takes up good positions when receiving passes and crosses into the area.
Reaction
Although there is an increased danger of being caught offside, the player advances more aggressively, making for more scoring opportunities.
Playmaking
When in possession of the ball, all other teammates become more adept at receiving passes.
Passing
When the player is in possession of the ball, his teammates will show improved movement off the ball.
Scoring
Shows better positioning and passing, and his shooting accuracy increases. Also, when COM controlled, he is more likely to go for goal.
1-on-1 Shot
Easier to score goals when 1-on-1 with the goalkeeper.
Post Player
When in possession of the ball up front, he is more able to hold the ball up for his teammates.
DF Positioning
Times his runs off the last defender better in order to evade the offside trap.
Shooting from distance
Becomes easier to take shots a fair distance away.
Side
The player, when COM controlled, utilizes the flanks more
Center
The player, when COM controlled, utilizes the middle of the pitch more.
Penalties
The player becomes better at taking penalty kicks.
1-Touch pass
Improves the accuracy of his one touch passing.
Outside of the boot
Increases the player's accuracy when using the outside of his foot.
Marking
Stays tight on the opponent he is marking.
Sliding tackle
Able to slide tackle well with less chance of committing a foul.
Covering
Becomes more skilled at covering for teammates defensively, especially when an opponents gets through.
DF Control
Defense becomes more coordinated, enabling better executed offside traps.
Penalty stopper
Ability to stop penalty kicks is improved.
1-on-1 stopper
As a goal keeper, will respond better to close range shots and will be harder to beat on 1-on-1 situations.
Long throw
Player will be capable of taking very long throw ins.
These are all from the in-game descriptions and as you can see leave some room for interpretation.