What this RewriteRule means/does?

Question

I have installed WordPress multisite on my server and I am under troubles with Apache, because for some reason doesn't read a CSS file, that exists, and the URL to this file is totally correct.

Due to this issue, I try to understand what the .htaccess file does and I have stack to this RewriteRule :

RewriteRule ^ - [L]

I know what the - and the [L] does but I cannot understand what the ^ does.

Just in case, the previews lines in .htaccess file are the following:

RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]

# add a trailing slash to /wp-admin
RewriteRule ^([_0-9a-zA-Z-]+/)?wp-admin$ $1wp-admin/ [R=301,L]

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d

Answer 1

This is shorthand for "in all cases". Mainly used with RewriteCond before.

Example:

# skip all files and directories from rewrite rules below
RewriteCond %{REQUEST_FILENAME} -d [OR]
RewriteCond %{REQUEST_FILENAME} -f
RewriteRule ^ - [L]

So, doing nothing in this case.