So I use my site + zenphoto as a replacement/easier access to imgur/sharing images faster as I use sharex. I also have a very long URL I want to shorten but have zero idea how mod_rewrite works and cannot find anything that helpfully explains or shows how it works. If someone can help me understand it that would be much appreciated.

Zenphoto includes the plugin tinyURL you can use to get a alternative shorter URLs to frontend pages for sharing. Use its method getURL() to get a short URL. See the in-file documentation how to use it. You may have to modify the theme used.

Another common way is to use a URL shortener service like bitly or others.