Hello,
macOS also includes a deep sleep mode known as Safe Sleep. Your Mac might enter Safe Sleep if your battery begins to run low, or your computer is left idle for a long time.
Safe Sleep copies the contents of memory to your startup drive and powers down the computer, allowing you to pick up where you left off without losing your work.
To wake your Mac from Safe Sleep, press its power button. If you use a Mac notebook and its battery is low, connect the AC adapter first.
When you wake your computer from safe sleep, a progress indicator appears. This indicates that the previously stored contents of memory are being read from the startup disk and copied back into RAM.
For normal Sleep mode, this is to save energy by putting your Mac to sleep when not using it. It's on but consuming much less power. It is also quicker to wake than if you restart your Mac. You can do this by going to Apple menu > Sleep.
To learn more, please check out: Use the Energy Saver settings on your Mac - Apple Support