There is a "show all file name extensions" option in Finder, but I don't recall if it's on by default or not as I haven't had to set up a fresh macOS install in a while and I've always had it turned on.

But, macOS isn't like Windows - the file extension doesn't matter. I can have a "file.txt" but it's actually a .xlsx excel workbook, and Excel will open it just fine (albeit, with a warning that the file extension doesn't match but that's dependent on the application presenting a warning). Windows actually uses the file extension to determine the type, macOS (and other *nixes) don't, they'll use some other file metadata. You can put whatever extension you want on a file, it doesn't matter except for determining what default app will attempt to open it when double clicking it in Finder.