Vim ! before execute silent '!mkdir' what is it for?

Question

Make new folder from Vim command line in Windows gVim

In this with the mkdir command a '!' is added in front of the command.

What does the '!' actually do?

Answer 1

The ! is for entering shell commands. In this case a command (mkdir) that would normally be entered at the windows command line.

More information available on the VIM documentation site

Answer 2

It tells VIM to run the command through a commandset:

Vim Cookbook

"The ! command tells Vim to run the text through UNIX command."

Edit: as JGB's link mentions, not UNIX directly

However, that is not always the case. Different placements can result in different things, as you have probably seen. You can see a lot of other options in this Stack Overflow question/answer set. (things such as force, toggle, etc.)