First you need to know The blockchain: basic technology of crypto currency

Crypto-currencies are all based on the same principle: the blockchain. Crypto currencies are a sequence of numbers stored on a computer in the form of block strings. The  principle is actually quite simple and particularly well explained in  the article published in Les Echos Bitcoin and crypto currencies, new  digital parts: "Take a database. Allow anyone to make changes to this database, only if you declare yourself a member. Put  in place a very long and very complex control procedure that must be  performed whenever a certain number ("block") of changes is requested. This procedure is carried out not by a single controller, but by all voluntary "members". Once validated, the "block" of changes is dated and added to the others in the registry. Finally, allow the registry to be read to everyone, and you have a blockchain database.  

 What's its use the cryptocurrency ? 

 Purchase of goods and services

As with any currency, crypto currencies allow the purchase of goods and services. Not  being under the control of a central authority and escaping any  regulation, they have long been the prerogative of illegal transactions  (ransomware, drug trafficking, etc.) but they tend to get rid of their  bad reputation by democratizing and attracting a wider audience. Crypto currencies are today more and more used for legal transactions.

Crypto currencies, like bitcoin, make it possible to buy many consumer goods. It  is for example possible to buy with bitcoins of course computer  hardware but also food, jewelry, decorative objects, cultural products,  etc. Overstock, a general merchant website, accepts payment in bitcoin, just like Shopify. Paying everyday goods with other cryptocurrencies is more difficult, but not impossible. The  ether for example could be used to buy works of art exhibited by young  artists at La Compagnie (Paris X) in the spring of 2017. The virtual  currency that wants to compete with Bitcoin has thus made its entry into  the real world. 

 Crowdfunding crypto-equity: another use of the virtual currency 

 Cryptocurrencies can also be used to finance businesses via crypto-equity crowdfunding. The process that is in its infancy is to finance equity-crowdfunding through virtual currency. This type of practice is referred to as ICO or Initial Coin Offering. Several platforms offer this solution such as Swarm.