As widely reported, and as promised by Elon, Twitter has published the code that manages what tweets show up on your timeline to the well known developers website, GitHub. Twitter put out a blog post explaining the decision. The blog post details what the algorithm evaluates when determining which tweets to feature in the For You timeline and how it ranks and filters them.
Video: Twitter in Plain English
From the archives: I found a great video by Lee Lefer over at YouTube. Its sort of a “Twitter for Dummies”–great primer if you’re still not quite sure what is the point of Twitter. [youtube=http://www.youtube.com/watch?v=ddO9idmax0o&w=425&h=344]