These days you may be confronting 3 different things.
There is the original vimscript (vimscript "classic") and that is all that I talk about.
There is now also vim9script -- which is part of regular vim, but must be explicitly enabled in your .vimrc file.
Finally there is NeoVim, which has replaced vimscript with the Lua language. I am not using NeoVim, so I have nothing to say about this.
Tom's vim pages / tom@mmto.org