What is a bitcoin?

Bitcoin is the first form of decentralized digital currency, created and held electronically, No one controls it. Bitcoins aren't printed (so it doesn´t have a bill like dollars or euros) they are produced by people, and increasingly businesses, running computers all around the world, using software that solves mathematical problems.

What is the difference between this and other currencies?

They can be used only to buy things electronically. However, the thing that is most valuable in the bitcoin is that no banks, government or other institution have any control over it. This puts some people at ease because it means that a large bank or group can control their money.

What is a bitcoin address?

A bitcoin address is an identifier which allows you to receive bitcoins to it or to send them from this. Just like PayPal, where you use your email address, but in this case, instead of having your nice little Email address, you'll have an address that looks more like a code (ex. 1LjM124N524NkgsNe5nM6067NLgua).

Right after you type that long code, you might as well verify it because these transactions are not reversible, so you have to be really carefully and double or triple check the address.

What is a private key?

A private key is a code that allows the user proves that he/she does really own this bitcoins. Every bitcoin address has a key, and these private keys are related to the bitcoin address. It is necessary to have both to use the bitcoin account. So the best you can do is keeping your private keys safe since anyone with that key can spend your bitcoins.

Is there a limit to the amount of bitcoins?

The number of bitcoins in existence will never be over 21millions. So they will keep gaining value over time since there is a limit on how much bitcoins there will be (unlike many other currencies that lose value over time).

How to earn a bitcoin?

You can buy or sell bitcoins in websites like www.bitxoxo.com/ or www.unocoin.com those two ones or the more used in India, or mine your own bitcoin via www.splititmining.com/? And follow the instructions.