<p>@Davide's answer is correct but I expand the explanation a bit particularly regarding the blockchain.</p>

<blockquote>
  <p>I´m beginner and I understood there is an unique huge common block chain to be used by world wide</p>
</blockquote>

<p>A crypto-currency like bitcoin requires people to run the bitcoin software that makes the whole system work; it is a <a href="https://en.wikipedia.org/wiki/Peer-to-peer" rel="nofollow noreferrer">Peer-to-Peer</a> (P2P) network and each machine running the software is called a <em>node</em>.** The primary incentive for people to run nodes is that they are getting rewarded with bitcoins via a process called mining explained <a href="https://bitcoin.stackexchange.com/questions/148/what-exactly-is-mining">here</a> and <a href="https://en.bitcoin.it/wiki/Mining" rel="nofollow noreferrer">here</a>. </p>

<p>A blockchain (aka ledger) is a data structure (think of it as a file in your computer) that stores a history of all the transactions (actually groupings of transactions, called blocks, i.e. forming a chain of blocks) that took place in the network. Currently, it is around 65 GBs big and it is getting bigger with time as new blocks (of transactions) are added. Each node has a copy of the blockchain which is the same in all nodes via a consensus process enforced by computer algorithms.</p>

<p>Thus, in bitcoin, there is one common blockchain with copies in each node.</p>

<blockquote>
  <p>and there a several different crypto currencies types by running on that . Am I correct? Thank you to all</p>
</blockquote>

<p>No, other crypto-currencies make use of different software, form their own P2P network and have their own blockchains. Similarly, those networks will have a common blockchain and each node will have a copy. </p>

<p>This is a simplified/high-level view but I hope it clarifies things a bit.</p>

<p>** Users that just want to use bitcoin do not need to run a node.</p>

CC BY-SA 3.0
2016-02-25T09:38:23.970Z
2016-02-25T09:38:23.970Z
2017-04-13T12:47:33.660Z
karask
<p>There are thousands of identical copies of the Bitcoin blockchain which is kept in sync worldwide thanks to its protocols. You can consider that like a single-instance super-redundant data structure. It store all the Bitcoin transactions. Then, based on the same idea, many project launched similar blockchains (sync-ed in a much smaller number of nodes though) that we can call AltCoins (alternative coins). Last, but not least, you can use the Bitcoin blockchain to define your own currency without the hassles of launching a new blockchain (and a new community). This last option is so called Coloured Coins. I suggest to Google the term.</p>

CC BY-SA 3.0
2016-02-23T21:42:24.293Z
Great - In fact my level of knowledge is still so low to understand 100% of answer, and all terms and concept. I want to thank you anyway. I ll keep trying to understand. Tks!
Minerando
CC BY-SA 3.0
2016-02-23T22:08:20.803Z
well, if you like the answer vote it. It is a way to incentivise people here
Davide C
CC BY-SA 3.0
2016-02-26T04:01:37.190Z
I don't think you made it very clear that there are many block chains, bitcoin is not the only one and many companies (ex banks) that are creating private blockchains.
Mark S.
CC BY-SA 3.0
2016-02-26T13:14:41.200Z
@MarkS. what words in the sentence "...many project launched similar blockchains (sync-ed in a much smaller number of nodes though) that we can call AltCoins (alternative coins)." are not clear?
Davide C
CC BY-SA 3.0
2016-02-23T20:34:47.840Z
2016-02-23T20:34:47.840Z
Davide C
<p>I´m beginner and I understood there is an unique huge common block chain to be used by world wide and there a several different crypto currencies types by  running on that . Am I correct?  Thank you to all</p>

<block><private-blockchains>
How many block chains exist?
Minerando
# How many block chains exist?

(Asked by: username_0 on 2016-02-23)

I´m beginner and I understood there is an unique huge common block chain to be used by world wide and there a several different crypto currencies types by running on that . Am I correct? Thank you to all

**Tags:** block, private-blockchains


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## 2 answers

### Answer by username_1 on 2016-02-25. Score: 5

@username_2's answer is correct but I expand the explanation a bit particularly regarding the blockchain.

> I´m beginner and I understood there is an unique huge common block chain to be used by world wide

A crypto-currency like bitcoin requires people to run the bitcoin software that makes the whole system work; it is a [Peer-to-Peer](https://en.wikipedia.org/wiki/Peer-to-peer) (P2P) network and each machine running the software is called a *node*.\*\* The primary incentive for people to run nodes is that they are getting rewarded with bitcoins via a process called mining explained [here](https://bitcoin.stackexchange.com/questions/148/what-exactly-is-mining) and [here](https://en.bitcoin.it/wiki/Mining).

A blockchain (aka ledger) is a data structure (think of it as a file in your computer) that stores a history of all the transactions (actually groupings of transactions, called blocks, i.e. forming a chain of blocks) that took place in the network. Currently, it is around 65 GBs big and it is getting bigger with time as new blocks (of transactions) are added. Each node has a copy of the blockchain which is the same in all nodes via a consensus process enforced by computer algorithms.

Thus, in bitcoin, there is one common blockchain with copies in each node.

> and there a several different crypto currencies types by running on that . Am I correct? Thank you to all

No, other crypto-currencies make use of different software, form their own P2P network and have their own blockchains. Similarly, those networks will have a common blockchain and each node will have a copy.

This is a simplified/high-level view but I hope it clarifies things a bit.

\*\* Users that just want to use bitcoin do not need to run a node.


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### Answer by username_2 on 2016-02-23. Score: 3

There are thousands of identical copies of the Bitcoin blockchain which is kept in sync worldwide thanks to its protocols. You can consider that like a single-instance super-redundant data structure. It store all the Bitcoin transactions. Then, based on the same idea, many project launched similar blockchains (sync-ed in a much smaller number of nodes though) that we can call AltCoins (alternative coins). Last, but not least, you can use the Bitcoin blockchain to define your own currency without the hassles of launching a new blockchain (and a new community). This last option is so called Coloured Coins. I suggest to Google the term.

> **Comments:**
> **username_0**: Great - In fact my level of knowledge is still so low to understand 100% of answer, and all terms and concept. I want to thank you anyway. I ll keep trying to understand. Tks!  
> **username_2**: well, if you like the answer vote it. It is a way to incentivise people here  
> **username_3**: I don't think you made it very clear that there are many block chains, bitcoin is not the only one and many companies (ex banks) that are creating private blockchains.  
> **username_2**: @MarkS. what words in the sentence "...many project launched similar blockchains (sync-ed in a much smaller number of nodes though) that we can call AltCoins (alternative coins)." are not clear?  

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