RH means "RedHat". It's a certification, but it's vendor-specific... you are certified for working with RedHat systems (Fedora Core, Enterprise, etc). This is most useful if you want to work with datacenters, which most often use either RedHat or "CentOS" distributions. If you want more general certifications, go with "LPI". You can find more at
Home - LPI -. The site will allow you to find approved testing centers in your area. Level 1 certification consists of 2 exams.