Check out this description that Rex posted recently in Linkedin:
"I have been struggling to learn social media for my business and professional use. I am finally beginning to be able to differentiate among the myriad sites. If you know the old television series, 'Gilligan's Island', then here is an easy way to keep the various sites straight:
Google+ is the Professor.
Facebook is Lovey Howell.
Linkedin is Thurston Howell III.
Pinterest is the Movie Star.
Tumblr is Gilligan.
Twitter is Mary Ann.
StumbleUpon is the Skipper."