I would also like to have a formal answer to what these are. There isn’t anything in the documentiation that actually states this.
The follow is my current estimation:
Considering there are “build targets” and using these as reference.
Targets doco: Targets | Unreal Engine Documentation
“WindowsServer” is the server target, with no client code.
“WindowsClient” is the client target, with no server code.
“WindowsNoEditor” is the “Game” build target version that cant run uncooked content (as the editor code is needed to load uncooked content)
“Windows” is the “Editor” target version that includes the editor code, so can load uncooked content.
“Windows” is much larger then “WindowsNoEditor”, WindowsClient, and WindowsServer versions, which would be explained by including the editor code needed to support uncooked content.