.htaccess is a special Apache file that tells your website how to function.
You can edit the existing .htaccess file on your site, or you can create a new text file in any directory and name it .htaccess
How can I secure my .htaccess file?
The file is already protected; it will be forbidden to browsers. To be very sure, double check that the file is named ".htaccess" and not "htaccess" nor "htaccess.txt". (It must start with a dot.)
Online Guides
If you do not code this file correctly, it can cause website errors.
Guides to dot-htaccess coding:
javascriptkit.com
apache.org
modrewrite.com
Great resource for mod rewrite lessons.
Great resource for mod rewrite examples.