If you haven't gotten in touch with Whisper just yet, it's a social network just like all other social networks. People express themselves, get into conversations with others, etc etc. But, what makes it so different is the fact that you do all these things while remaining anonymous.
Lots of people stay guarded when posting on social networks because they fear judgment and criticism. With Whisper, that anxiety goes away because no one will ever know who you are. While Whisper's anonymity can give people a platform to talk about things they're too scared to publicly, it also allows people show their worst thoughts, as these disturbing posts about Islam show: