TLDs are such domain extensions as .com, .org, .net, .info, .biz and more. They are so-called top level domains, because the are very popular, demanded and recognizable. Other TLDs include .edu for educational institutions, .mil for military, .museum for museums, and .post for postal services. Even between these TLDs there are price differences. The most sought after domain extension is .com and therefore costs the most. The price range is relative to the demand of each domain extension.