What, exactly, is blockchain? Blockchain is a rapidly increasing list of records that are linked to each other via cryptography. In simple terms, a blockchain is a record of a particular transaction that is encrypted, secured, and linked to other transactions.
When blockchain started out, it didn't gain much ground. However, by 2017, it was hard not to pay attention to a market that had increased in value by around 50 times over the course of 12 months, from around 15 billion US dollars in January, 2017, to over 830 billion US dollars on 7 January, 2018.
These are eye-watering numbers, but they only represent the value of publicly traded cryptoassets (meaning the currencies that are in circulation), and not the entire supply! A lot of the supply is still locked away and kept by the founding teams, which helps to make Bitcoin as secure as it is now. You will learn more about this in later chapters of this book.