Every plugin and digital processor adds some latency. A linear-phase EQ might add 50ms of delay; a lookahead limiter adds 1–5ms. Without delay compensation, tracks with heavy processing play slightly later than unprocessed tracks — causing phase issues and timing drift.
All professional DAWs include Automatic Delay Compensation (ADC). It measures each track's total plugin latency and delays all other tracks to match. ADC can typically compensate for thousands of samples of delay. When recording, ADC is often disabled to minimize monitoring latency, then re-enabled for mixing.