Snapchat is a photo messaging (Photo Sharing for Instant Messaging) application developed by Evan Spiegel, Bobby Murphy, and Reggie Brown, then Stanford University students. Using the application, users can take photos, record videos, add text and drawings, and send them to a controlled list of recipients. These sent photographs and videos are known as "Snaps". Users set a time limit for how long recipients can view their Snaps (as of April 2014, the range is from 1 to 10 seconds), after which they will be hidden from the recipient's device and deleted from Snapchat's servers (Self Destruct). http://en.wikipedia.org/wiki/Snapchat
Original notorious use: sexting.