Debride or Debridement in medical terms is when a doctor removes dead, contaminated, or adherent tissue and/or foreign material.
To debride a wound means to remove all materials that may promote infection and impede healing.
This debridement and removal of materials from your skin may be done by enzymes as with proteolytic enzymes, mechanical methods as in a whirlpool, or sharp.
Debridement when done by a doctor is usually not painful as you will be given pain medication or in more severe cases of medical debridement you are usually given anesthesia for sedation.
If it's done naturally then you may experience a little pain but taking some pain medicine can help with the pain.