Bitcoin is a digital currency and payment system that was introduced in 2009 by an anonymous programmer (or programmers). Over the past few years, it has attracted tremendous interest from programmers and finance-enthusiasts. It has spawned the introduction of other alternative currencies and distributed ledger systems.

Bitcoin's design is fundamentally different from cash and online money because there is no central authority that issues or regulates the currency. This gives rise to several challenges, and the bitcoin protocol elegantly addresses many of them.

In this module, we will begin with understanding centralisation, as it applies to normal currencies. We will then talk about the issue of identity on the bitcoin network, and how one can send/receive bitcoins. Broadly, this module deals with what a bitcoin is, the next module deals with how it works, and the last module deals with why it is designed the way it is.