I often like to utilize Category Pages as navigational pages and resources within my site organization. Some themes will display the description by default and in the past I have custom coded category template pages individually as I had the time using the Wordpess codex. I think every category page should have some constant text that can be used for introducing the dynamic archive that follows and gives some meat to use for SEO.
When I originally started adding this feature to sites I would use a custom snippet in the category template that allowed for every category, I was not aware that a description could be pulled from internal settings. This is much easier.
This is all I need to know:
