This document provides an overview of Bitcoin and blockchain technology. It defines Bitcoin as a decentralized digital currency operated through blockchain technology without a central authority. Blockchain solves the "Byzantine General's Problem" of reaching consensus in a decentralized network by distributing a ledger of transactions across many computers. While Bitcoin and blockchain offer innovations, they also enable crimes on the dark web like drugs, weapons and murder. The future of Bitcoin and its value are uncertain, but the technology may fundamentally change how people interact globally.