What is 140?
The maximum number of characters allowed in a tweet, which is a single message on the Twitter social network.
This 140 character limit has given rise to a twitter-based expression derived from 411. "The 411" being a phrase that means "information," "summary," or "low-down," 140 is the Twitter equivalent. You could say "The 140" is the twitter equivilant of "the Reader's Digest version;" it's the summary or gist of something that can fit within the bounds of a tweet.
Charlie: @Echo Hey, did you hear about that newfangled thing?
Echo: @Charlie No, I didn't. What's the 140?
Charlie: @Echo It's harder better faster stronger!