A sleep cycle refers to a period during which an individual goes through several stages of sleep, including light sleep (NREM), deep sleep (N3) and REM (Rapid Eye Movement) sleep. A complete sleep cycle typically lasts for approximately 90 minutes, with each stage of the cycle lasting for different durations throughout the night. The body goes through several cycles during a single night's rest, with the number of cycles varying between individuals and depending on their age, health status, and other factors. Understanding one’s sleep cycle can help in identifying any disruptions or issues related to sleep quality, which may require intervention or lifestyle changes for better rest.