the short answer
A deload week is a planned period, usually seven days, where you deliberately reduce training stress so the body can recover from accumulated fatigue. You typically keep the same exercises but cut working volume by roughly half, lower the load, or both. The point is to let strength that fatigue has been masking surface, so the client returns refreshed and ready to push the next training block rather than grinding into a stall or injury.
This article is general training information for coaches, not medical advice - recovery needs vary by individual, and persistent pain or fatigue should be checked by a qualified clinician.