A deliberately lighter week with volume or intensity clearly reduced, so adaptation can catch up.
You don't get stronger during training, you get stronger recovering from it. When stimulus arrives faster than your body processes it, fatigue accumulates: performance drops even though you're doing more. A deload every four to eight weeks — roughly half the volume at similar loads, or the same volume at 60–70% — lets fatigue drain away while the adaptation stays. Typical warning signs beforehand: nagging joints, worsening sleep, warm-up sets feeling heavier than last week's working weight. People who think deloads are a waste of time eventually take one involuntarily — it's called an injury layoff.