Glossary — ChessInspect

Your report speaks a chess coach's language. Don't worry if a word is new — everything is defined here, in plain English. Come back to it as often as you need.

How the report measures your moves

Engine (Stockfish): The super-strong chess program that analyzes your games. For every position it finds the best move and scores the position. It's what judges your moves — not an opinion.
Evaluation (“eval”): The score the engine gives a position, in pawns. +1.0 means White is a pawn's worth ahead; −2.0 means Black leads by two pawns; 0.0 is equal. When the eval slides from +0.3 to −1.4 after your move, you just handed over a piece-and-a-half's worth of advantage.
Centipawn: One hundredth of a pawn — the engine's fine unit. 100 centipawns = 1 pawn. It measures small edges a half-pawn couldn't. “You lost 170 centipawns” = you gave up 1.7 pawns' worth on that move.
ACPL (average centipawn loss): The average you lose per move versus the engine's best move. Lower is better. Rough bands: under 20 = master level; 20–40 = strong club; 40–80 = intermediate; 80–150 = developing; over 150 = lots of leaks. It's your overall accuracy in a single number.
Inaccuracy · Mistake · Blunder: The three severities of a bad move, from mildest to worst, by how much eval you lost. An inaccuracy is lukewarm, a mistake is costly, a blunder can flip the game. The report counts how many you make per game.
Costly move: One of the moves that lost you the most eval across the games analyzed. The report lists them with the move you played, the engine's move, and the eval before/after — so you see the exact moment it turned.
Engine move (best move): The move Stockfish judged best in the position. It's compared to what you played to measure the gap.
Forced mate (missed mate / allowed mate): A sequence that leads to checkmate no matter what the opponent does. A missed mate = you had a forced mate and didn't play it (a calculation/vision issue). An allowed mate = you let the opponent mate you by force (a king-safety and alertness issue).

Leaks — where you lose points without noticing

Leak: A recurring way you bleed eval, game after game. A tactical leak comes from blunders in concrete, calculable lines. A strategic leak is sneakier: you don't blunder, but your position slowly rots from poor plans. The report names your main leaks.
Positional drift: The slow eval loss on quiet moves (no capture or direct threat), phase by phase. It's the silent strategic leak: no spectacular blunder, just slipping a notch each move for lack of a plan. High drift with few blunders = your problem is the plan, not calculation.

Phases of the game

Opening: The start of the game: you develop your pieces, castle, fight for the center. Roughly the first 10–15 moves.
Middlegame: The heart of the fight once pieces are out: attacks, plans, tactics. This is where most games are decided.
Endgame: The final phase, when few pieces remain: kings become active and every pawn counts. Technique matters more than raw calculation.

The clock

Time pressure (time trouble): When you have little time left (the report counts moves played under 30 seconds). Many players lose most of their points here. If your accuracy drops sharply under pressure, it's the clock costing you — not your chess level — and that's fixable with a pacing routine.

Tactical motifs

Tactics: Short, forcing, calculable sequences that win material or deliver mate. You spot and calculate them move by move.
Combination: A forced sequence, often involving a sacrifice, that leads to a clear gain (material or mate).
Threat: A move that sets up winning something next move unless the opponent responds.
Fork: One piece attacks two targets at once. The opponent saves only one — you win the other. The knight is the king of forks.
Pin: A piece can't move because a more valuable piece (often the king) sits behind it. It's “pinned” in place.
Skewer: The reverse of a pin: a valuable piece is attacked first, must move, and steps aside to expose a piece behind it that you then capture.
Discovered attack: You move one piece, and that move unveils an attack from another piece behind it. Two threats in one.
Double attack: Attacking two things at once (by one piece or a discovery) so the opponent can't parry both.
Sacrifice: Deliberately giving up material to get more in return: a mate, a decisive attack, or a bigger gain.
Checkmate: The king is attacked and has no square to flee to and no piece to block. The game is over.

Strategic concepts

Strategy: The long-term plans, as opposed to move-by-move tactics. “Strategy creates the opportunities; tactics turn them into a win.”
Piece activity / mobility: The number of useful squares your pieces control. Active pieces press on the game; passive ones (few squares) play short-handed. The report compares your mobility to your opponents'.
Piece coordination: Your pieces working together toward one goal, rather than each off on its own.
Pawn structure: The arrangement of your pawns. It dictates the plans: where to attack, which squares are strong or weak. Pawns never move backward, so their structure shapes the game for the long haul.
Space: The territory your pawns and pieces control. More space = your pieces breathe while the opponent's are cramped.
Outpost: An advanced square (ideal for a knight) that enemy pawns can no longer attack. A piece there is firmly planted and very annoying.
Open file: A file with no pawns on it. It's the highway for rooks: whoever controls it invades the opponent's camp.
King safety / pawn shield: How sheltered your king is, especially behind the pawns protecting it after castling. A cracked shield = attacks get through.
Castling: The special move that shifts the king two squares and brings a rook beside it, to tuck the king away and activate the rook. Not castling (or castling too late) often leaves the king stuck in the center, exposed.
Initiative: Being the one calling the tune: stringing together threats and forcing the opponent to react to your moves instead of playing their own.
Prophylaxis: Preventing the opponent's plan before pushing your own. You ask “what does he want to do?” and defuse it.
Passed pawn: A pawn that no enemy pawn can stop on its way to promotion (becoming a queen). A major asset, especially in the endgame.
Pawn weakness: A pawn that's hard to defend: isolated (no friendly pawn beside it), doubled (two on the same file), or backward. It becomes a lasting target.
Bishop pair: Having both bishops when the opponent has only one. In open positions it's a real edge, since bishops sweep the board from long range.
Conversion: Turning a winning position into an actual win — or saving a losing one. The report measures how often you cash in your advantages.
Tempo: One “unit of time” = one move. Gaining a tempo means making progress while the opponent wastes a move (for instance, having to move the same piece twice).
Endgame transition: The moment you trade the last heavy pieces to enter an endgame — often a strategic choice (simplify when ahead, avoid it when behind).

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