Piece activity
Piece activity describes how much influence a piece exerts, measured by the squares it controls, the targets it eyes and the freedom it has to move, so an active piece is worth more than its nominal value.
Also called: active pieces
A piece is active when it sees many squares, stands on a good post and takes part in the fight. A bishop on an open diagonal aimed at the enemy king is active, while the same bishop locked behind its own pawns is passive. The nominal values of pieces are averages, and activity is what moves a piece above or below that average.
Several things raise activity: open files for rooks, outposts for knights, long diagonals for bishops and a central, safe square for a king in the endgame. Trading is often a tool for this, because you can swap your passive piece for the opponent's active one, or free your game by removing a piece that cramps you.
When you evaluate a position, count activity before material. A side that is a pawn down may be better if every piece is working while the opponent's are tied up defending. In rook endgames especially, giving up a pawn to free a passive rook is often the right choice.
The common error is to place a piece on a square that looks impressive but has no targets, or to retreat a good piece for safety when it was doing real work.
A neighboring idea is Piece domination. Piece domination is a position in which an enemy piece cannot move without being captured, because your pieces control every square it could go to, so it is stuck and out of play.
Also worth reading is Active rook. An active rook controls open lines, attacks enemy pawns or the king from behind or the side, and cannot easily be attacked, which makes it far stronger than a rook that merely sits and defends.
Also worth reading is Dynamic play. Dynamic play is a style of handling a position that prizes activity, initiative and fast-changing threats over lasting structural features, accepting concessions such as weaknesses or material in return for time and attacking chances.
Where "Piece activity" fits your own play is easier to judge with a coach reading your games; the first lesson is a paid one-on-one review that ends in a written plan.
Related terms
The worst-placed piece is the piece in your position doing the least, and improving it by rerouting it to a better square is a standard way to make progress when no immediate tactic or break exists.
Piece coordination is the degree to which your pieces support one another and work toward the same target, so their combined force is greater than the sum of what each could do alone.
An outpost is an advanced square, usually in the opponent's half of the board, that is protected by one of your own pawns and cannot be attacked by an enemy pawn.
An open file is a vertical column of the board with no pawns of either color on it, which gives rooks and queens a clear path to invade the opponent's position.
An active rook controls open lines, attacks enemy pawns or the king from behind or the side, and cannot easily be attacked, which makes it far stronger than a rook that merely sits and defends.
Piece domination is a position in which an enemy piece cannot move without being captured, because your pieces control every square it could go to, so it is stuck and out of play.
Guides that go further
What to decide first, the questions to ask, what a first lesson should show and the red flags to avoid.
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A game review, a read on your level and a written study plan from George Li.
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