This video explains what Snapchat is all about. You take a photo, send it to someone and ten-seconds later it has disappeared forever. No saving them, no forwarding them on. This app is built to capture a moment and share it in a similar way to speech.
We connect to friends by either searching for their Snapchat using their name, or by allowing the app to match the contacts in your address book with users in its database. This allows you to connect with strangers, but you will need to know their username as a minimum requirement.