In the context of the cryptocurrency industry, a whitepaper is often published prior towards launching a crypto/blockchain project to explain the issues that the project aims to address as well as the steps it will take towards addressing it.
The foremost whitepaper that kickstarted the tradition of publishing a whitepaper along with lauching a project is the renowned bitcoin whitepaper published in October 2008 by the pseudonymous Satoshi Nakamoto. Which succintly explained the need for a peer-to-peer digital cash system and how bitcoin will function in 8 short pages.