Oh my goodness, I don't know what I was thinking. I was just helping a Chinese user, and by habit, I went through the trouble to translate the content into Chinese, and changed the link to Chinese locale for you. I am so sorry.
https://learn.microsoft.com/en-us/windows-serve...
GAC:
Generally Available Channel, which means the latest version of Windows is being used.
LTSC:
Long-Term Servicing Channel, a version of Windows designed for stability that receives fewer feature updates but is generally supported for a longer period of time.
ESU:
Extended Security Updates, a paid option that allows users to receive security updates for a version of Windows after it reaches its end-of-life date.
So these really define the difference of supporting. GAC is the most common ones out there for consumers.