What's the difference between ':source file' and ':runtime file' in vim?

Question

I saw this command in the /etc/vimrc file on my system:

runtime! vimrc_example.vim

From the docs:

:ru[n

Answer 1

:source sources the file specified by the path given (relative or absolute)

:runtime sources the first file (unless banged!) found in &runtimepath that matches the partial path given.

BTW, the pathnames used with :runtime can contain wildchars (somehow a glob-pattern). This has nothing to do with regexes.