A deload is a deliberately lighter training week with fewer sets and less effort. The goal is to let your body recover from accumulated fatigue so you can make progress again afterwards. You keep training, just with far less load.
When a deload makes sense
Muscles grow between sessions. More sets only help as long as you recover from them. Typical warning signs are performance that drops over several sessions, joints that hurt persistently, and soreness that has not faded by the next session for the same muscle. Then a lighter week is usually the better choice than adding another set.
What a deload looks like
A simple scheme: if performance drops over two to three sessions, plan a week with half the sets and more distance from failure, around RIR 3 to 4. Keep the exercises the same so you keep the movement pattern.
Example: If you normally do 16 hard sets per week for your back, the deload week has 8 sets that end with 3 to 4 reps in reserve. These numbers are an example.
Use this time to check what is happening outside the gym too. Sleep and calories play a big role in recovery. In a cut, falling performance is often a sign that the deficit is too large, not that the training is the problem.
What a deload is not
A deload is not a fix for persistent pain. Pain is not a training stimulus and should be checked by a doctor. Nor is it something you must do on a fixed calendar: if your training is going well and performance keeps rising, you do not need one.