Complex sentence: Snapchat provides a service where people can send photos and videos to other users privateley and for a short period of time (which is later erased), but there has been a revelation that they did not vanish after viewing.
Split into simpler sentences: Snapchat provides a photo messaging service where people can send photos and videos to other users privately for a short period of time (which is later erased). Lately there has been a revelation that they did not vanish after viewing.