What does that mean? Specifically, the :%!.
How to use an external command in Vim to modify selected words and lines?
pipes the current file's contents to command's stdin.
So, :%! sort is pretty much the same as (from a shell) cat file | sort.
How can I insert text from the command prompt?
How can I run a batch file in Vim's console?
What does :[range]t <line-number> do?
What encoding does :! use?
Can I open a file at an arbitrary line and column via the command line?