In BDSM, aftercare is the period of time after a scene in which partners attend to one another's physical, emotional, and psychological needs. Typically, the dominant partner in the scene will be the one caring for the submissive partner or partners. BDSM scenes are often very intense, and can often be emotionally and psychologically draining. Physical injuries are also not uncommon during these scenes.
More About Aftercare
Physical injuries inflicted during a BDSM scene obviously need to be attended to, but aftercare is also about emotional healing and reconnection after a scene. During the period of aftercare, partners will often chat and snuggle. The partner acting as a dominant will also often praise their submissive and reaffirm their importance. Aftercare is a very individual experience, however, and some submissives may prefer to take this time to be alone and tend to their own needs.