Technorati Authority is the number of blogs linking to a website in the last six months. The higher the number, the more Technorati Authority the blog has.
Technorati Rank is calculated based on how far you are from the top. The blog with the hightest Technorati Authority is the #1 ranked blog. The smaller your Technorati Rank, the closer you are to the top.
Vía: Technorati Blog