Cryptocurrencies are fairly new. To start with, you should know that cryptocurrencies are not the same as any digital currency that we have. The earlier versions were centralized but cryptocurrencies today are not. The most well-known cryptocurrencies are Bitcoin and Ethereum.
Interestingly cryptocurrencies were not meant to be the way it is today. It was invented by Satoshi Nakamoto who aimed to create an electronic way to send cash from one to the other. There were always concerns with decentralization and people wanted some way to ease the digital way of transacting cash.
The cryptocurrency applied maths and computers to solve the shortcomings that were therein fiat currencies.
Dating back to the 1980s
The technical foundation of cryptocurrencies dates back to the 1980s. That was the time when David Chaum who was a cryptographer invented an algorithm that is the main version of the modern encryption. The system was such that it allowed information exchange in secure and unadulterated format. This led to the scope of electronic transfers in the future. This got was popularly known as blinded money.
It was followed by enlisting another cryptocurrency enthusiastic to commercialize the concept. This led to the invention of DigiCash which was a for-profit company that made units based on this blind algorithm. TheDigiCash was not decentralized and had government control. The company, however, had an upper hand on the supply the same way in which banks have an upper hand on the fiat currency.
Satoshi Nakamoto understood that starting a new online system that was centralized would give him no results. So he decided to create a system that was digital and had no control of the government. Thus it was totally decentralized. This currency was Bitcoin. This was the first decentralized currency that was not controlled by any governing body or bank. The only one who had control on it was the Bitcoin community.
Bitcoin was created in the year 2008 and after that its value exploded. When Bitcoin was created it was worth some cents. However the value grew exponentially and in the year 2017, a single Bitcoin was priced around $7500. Bitcoin thus grew to a monumental level in the last few years.
After this, many new cryptocurrencies were invented which improvised on the bitcoin algorithm. And yes it is no rocket science to know that those who had invested into Bitcoin at an earlier stage became rich overnight.