Threefold repetition is a draw rule: if the exact same position occurs three times in a game, with the same player to move, a draw can be claimed.
The positions don’t have to happen on consecutive moves — they just have to be identical, with the same side to move, the same piece placement, and the same castling and en-passant rights. When that position appears for the third time, either player may claim a draw.
The most common way it arises is perpetual check: a player who is losing keeps checking the enemy king, which is forced to shuffle between the same squares. Neither side can make progress, and the position repeats until the game is drawn.
Online, the draw is usually awarded automatically. Over the board, you must claim it — typically by stating your intended move and announcing the repetition to the arbiter before playing it.
No. The three identical positions can occur at any points in the game. What matters is that the position — including whose move it is and the castling and en-passant rights — is exactly the same all three times.
Perpetual check is a common cause of repetition, but they aren’t identical. Repetition can happen without any checks; perpetual check is simply one forcing way to make the same position keep returning.
BetterChess is a practice tool — we make no guarantee you'll reach 1800 or any rating. Definitions are standard chess terminology; every diagram position is checked legal with the same engine the board runs.