- something that is used as a medium of exchange; money.
- general acceptance; prevalence; vogue.
- a time or period during which something is widely accepted and circulated.
- the fact or quality of being widely accepted and circulated from person to person.
- circulation, as of coin.
A cryptocurrency (or crypto currency) is a digital asset designed to work as a medium of exchange using cryptography to secure the transactions, to control the creation of additional units, and to verify the transfer of assets. Cryptocurrencies are classified as a subset of digital currencies and are also classified as a subset of alternative currencies and virtual currencies.
Bitcoin, created in 2009, was the first decentralized cryptocurrency. Since then, numerous cryptocurrencies have been created. These are frequently called altcoins, as a blend of bitcoin alternative. Bitcoin and its derivatives use decentralized control as opposed to centralized electronic money/central banking systems. The decentralized control is related to the use of bitcoin’s blockchain transaction database in the role of a distributed ledger.
Unlike centralized banking, like Bangko Sentral ng Pilipinas, where governments control the value of a currency like Pesos through the process of printing fiat money, government has no control over cryptocurrencies as they are fully decentralized.
Most cryptocurrencies are designed to decrease in production over time like Bitcoin, which creates a market cap on them. That’s different from fiat currencies where financial institutions can always create more, hence inflation. Bitcoin will never have more than 21 million coins in circulation. The technical system on which all cryptocurrencies are based on was created by Satoshi Nakamoto.
Fundings – ICOs
An Initial Coin Offering (ICO) is an unregulated means by which funds are raised for a new cryptocurrency venture. An ICO is used by startups to bypass rigorous and regulated capital-raising processes required by venture capitalists or banks. In an ICO campaign, a percentage of the cryptocurrency is sold to early backers of the project in exchange for legal tender or other cryptocurrencies, often Bitcoin or Ethereum.
How many cryptocurrencies are there?
This is a list of cryptocurrencies. The number of cryptocurrencies available over the internet as of 27 November 2017 is over 1,324 and growing. A new cryptocurrency can be created at any time. By market capitalization, Bitcoin is currently (2017-August-19) the largest blockchain network, followed by Ethereum, Bitcoin Cash, Ripple and Litecoin.
References:  Wikipedia  Blockgeeks