What is the importance of your Haplogroup?  From the Wheaton Surname Resources, Lesson 04:  "Even if two men have the same values on 67/67 (67 of 67) markers they cannot be related in the past 1,000 years if they belong to different haplogroups."  Haplogroups are the major branches of the male evolutionary tree.  Through time, mutations occur, and these are termed SNPs when they reach a given level of occurrence.  Testing is uncovering more SNPs constantly, and figuring out where these fit on the tree's branches and twigs is not always up to date.  Naming them is still another challenge.  For a good review of genealogical genetics with many additional links, see the Wheaton Project:  https://sites.google.com/site/wheatonsurname/beginners-guide-to-genetic-genealogy

CeCe Moore has a blog post discussing the competing naming conventions for YDNA SNPs:  http://www.yourgeneticgenealogist.com/2012/09/lets-all-start-using-terminal-snp.html