While using snapchat, a person can take a picture, put a timer on it, ( to make it visible for a certain amount of time: 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 seconds) and then you can add a note if you want and then can send it to anyone if you have their snapchat username.
Parents would want to be careful to let their child use this app, because there is the possibility of a kid taking innapropriate pictures or adding bad language to the pictures, and the parent would never know because the picture disappears in seconds and you can never find it again. I use it with my friends just for fun, and my parents trust me with what I do with it, and they occasionally look at the pictures my friends send me.