Tick

A tick is the smallest unit of price movement in a concentrated-liquidity pool. Prices are quantized to discrete ticks, and a position’s range is defined by a lower and upper tick. Each fee tier has a tick spacing that sets how granular ranges can be.

On Uniswap V3, every pool has a fee tier with an associated tick spacing (wider spacing for higher-fee, more-volatile pairs). Your liquidity range snaps to tick boundaries, so a "range" is really a lower tick and an upper tick.

Ticks matter for automation because the keeper re-centers a position by choosing new lower/upper ticks around the current price.