Edlin is a line editor, and the only text editor provided with early versions of IBM PC DOS,[1] MS-DOS and OS/2.[2] Although superseded in MS-DOS 5.0 and later by the full-screen MS-DOS Editor, and by Notepad in Microsoft Windows, it continues to be included in the 32-bit versions of current Microsoft operating systems.
edit: link and explanation of syntax used if anyone is interested. the w (write) and q (quit) commands made it somewhat similar to VI(M).
https://www.computerhope.com/edlin.htm
That tool was only included with Windows XP Professional, and even then, it was a command-line utility—so unless you were specifically looking for it or browsing through the %windir%\system32 directory, you probably wouldn’t have noticed it.
The article I referenced didn’t specify exactly which 32-bit versions it came with or when it was removed—it just mentioned that it was still included in 32-bit Windows after the DOS era. I didn’t write the article myself, so I can’t really speak to its accuracy.
Personally, I used that edline a lot back in the DOS days starting around 1985, until I switched to Notepad in Windows 95 and later to VIM when I moved to Linux after Windows 98. I never really checked for it in newer versions of Windows after that. A quick Google search confirmed it wasn’t included in XP Home, which would explain why you never saw it.