This explains all terms used:
Vim’s built-in scripting language, VimL. This language is also known as Vimscript. Depending on how you look at it, either VimL is an alternate name for Vimscript or Vimscript is an alternate name for VimL.
Actually, there’s no real official name for the language; the closest seems to be the two-word “Vim script.” To better follow English naming conventions, this is usually altered to “Vimscript,” or more rarely, “Vim Script”—but all of this can be confusing, since the files which store code in this language are themselves called “Vim scripts.”
The relatively new name “VimL” (“Vim Language”) has been gaining in popularity in rough correlation with the growth of the code-sharing site GitHub. Its use is a matter of preference, but I do find it more easily distinguishable from mentions of Vim scripts or of writing generic scripts using Vim (in search results, for instance).
Read more - https://pragprog.com/book/bkviml/the-viml-primer