Blogs.magicjudges.org is a WordPress MultiSite network, or a group of sites all running off of one WordPress installation. Each site lives at a URL that begins with http://blogs.magicjudges.org and is followed by the site’s slug, for example http://blogs.magicjudges.org/rulestips and http://blogs.magicjudges.org/jotw.
Each site operates pretty independently: when you write content for your site or make changes to your site, it won’t affect any other sites.
User accounts are shared across all sites on the network, so you’ll only ever need one account to log in. However, users can have different roles (and thus different capabilities) on different sites.