The original idea was to have short messages that disappear after being read so that people only send you relevant details.
I want to add more features and more way to communicate in the future.
The fact that it doesn't tell you when someone is typing and you don't get notified when someone unsends a message reduced a lot of anxiety.
I'll try my best to answer your questions.
The target user is anyone who wants to communicate without worrying about message permanence or risk being tied to the message they sent.
The sender's details are not included when a message is viewed making the app screenshot friendly. Screen recording won't get you very far either.
Coincidentally, the way in which the app was designed solves many privacy concerns highlighted in Zuckerberg's privacy manifesto - https://www.facebook.com/notes/mark-zuckerberg/a-privacy-foc...
I feel like I couldn't use this for serious messaging (things closer to email), but also that it's too limiting for my frequent communication with my partner and close friends or family. There are elements of Snapchat in this, but my impression of Snapchat was that the success was in large part because the pressure of crafting a great photo for FB/IG was lessened. Do people have that anxiety with text? I'm not sure.