If you track your sleep with a wearable or any other device you might hear about "REM", "Light", and "Deep" sleep. Sometimes, this can be confusing. I'm here to break it down.
First, is the "Awake" stage. A sleep foundation report states that this is the time when people doze off and typically lasts one to five minutes. Your body is not fully relaxed yet, but you are in the process of relaxing. This stage may also cause you to twitch, which is normal. If you're looking to wake someone up, this would be the stage. You can easily get up in this position since you're not asleep.
"Light sleep" is the second stage of sleep. In this state, your body lowers its temperature, slows its breathing, and slows your heart rate. Brain waves will also have a unique movement, and eye movement will come to a complete stop. You will also experience short bursts of activity from your brain to keep you from waking up as a result of certain forces. For example, that neighbor still has a party going on. In one cycle, this will typically last 10-25 minutes.
As we progress through stage three to "Deep sleep", more restoration occurs. Muscle tone, pulse, and breathing rate are even slower. Most scientists can agree with this being the most significant part of sleeping, as it contributes to critical thinking and creativity. This stage lasts about 20-40 minutes but gets shorter as you sleep.
As you wake up in REM, your body gradually returns to normal. This stage is required for better cognitive functions such as memory, learning, and creativity. You tend to have vivid dreams at this stage, as you are recalling memories from the previous day. This makes up about 25% of your sleep.
These stages happen in cycles, so after you hit REM, you might wake up, then drift back into NREM sleep.