What is a private key (private keys) Bitcoin?

Transfer or move the Bitcoin is indeed very easy, but in the rear screen, movement and storage of Bitcoin is actually done with something called the ' private key '. The easiest way to fully understand this, is to imagine a traditional post box system:

Imagine if Maria wanted to send a letter to Peter. First of all, he needs to know the address or number of the post Peter. Vice versa, if Maria wanted to send the Bitcoin to Peter, he must know the address of the Bitcoin Peter, that is the number that specifically indicates that the mailbox belongs to Peter. This number is called with the address of the wallet (wallet address), or the public key (public key). This number is very long and complicated because of the many mail boxes Bitcoin on the world, but fortunately you don't need to stop, you can see it on the internet.

So now Mary sends Bitcoin to postbox Peter. Let's suppose the number mail boxes Peter is 2034. Maria can look into this and see postbox Bitcoin therein, even all the people passing by can see p.o. box 2034 containing a Bitcoin. The interesting part about this is Bitcoin-where everyone can see all transactions without knowing the identity of the owner. One can see there a Bitcoin in 2034, yet no one, except Mary and Peter, knowing that the mailbox belongs to Peter.

Now let's look at how Peter taking the Bitcoin-he can see him there, so he did not need to do anything. But if he wants to move it, he needs to make that box to send it to other people. To open this post box it requires a key-and this is the unique key belongs to him, also called the private key. Only Peter can use this private key to open his mailbox. When he opened it, he can move the Bitcoin and put it into the mail boxes of other people. Suppose he bought the game online at Microsoft, he may enter into the box belonging to the Bitcoin Microsoft and if Microsoft viewed Bitcoin they receive, they will send you the online gaming to Peter.
If Maria sends Bitcoin to the wrong post box, he can't take it back. This is the same as cash-if you have been paying out to someone, you can't take it back easily. No one can move the Bitcoin, except Peter, who had a key to the post it. If Peter lost the key? Then there will not be anyone who can access the post it, forever! Peter should make sure that no one is stealing the key, because if the people could open the box belonging to Peter and steal Bitcoinnya. So it is important to keep it as safe as possible keys, or entrust the keys to the person who can do it.

The private key gives access to the system of the Bitcoin Bitcoin.

Additional materials
What is a Bitcoin Private Key, How to Use It, Keep it Safe!