This document is a series of slides from a presentation by Sam Wouters on blockchains and bitcoin. It discusses the key differences between open and private blockchains, how blockchains work through decentralization, immutability and other principles, and potential applications of blockchain technology beyond digital currency, including for finance, supply chains, identity and more. It argues that open blockchains have advantages over private blockchains in fostering innovation, though private blockchains may have some uses for internal networks.