Crypto-currency is an attempt to replace money transactions with a digital medium of exchange using peer-to-peer networking. Bitcoin was the first and still the most popular altcoins of all cryptocurrencies.
There is short video about what bitcoin is:
Yuo can use bitcoin for buying many things and services online. Also gaming or betting on sports online.
Here is a list of trusted casinos where you can play using altcoins like bitcoin online.
How to deposit to bitcoin casinos and booking sites?
How to withdraw from online casino to bitcoin wallet?