3 user vs. 1 user / 3 pc

If this question is already answered, I’m sorry I couldn’t find it.

 

Amazon.com has two versions listed:


1. Norton Internet Security 2009 - 3 User Edition ($61.59)
2. Norton Internet Security 2009 - 1User/3Pc ($51.99)

 

Are there two different versions?
If so, what’s the difference?