# Chapter 2 - Apps on Blockchain

###### tags: `Module 0`

### Intro
In the previous chapter, we understood how Blockchain can solve the problems in the current financial system. And also, how that's only the first problem that blockchain solves, there's much more to explore and innovate in the future - even Cryptobots running on top of a blockchain network 😝!

### Study time

Blockchain is a network, similar to how the railway system is a network.

The Railway system runs on top of the protocol called **railway tracks**.

A protocol is simply the underlying set of rules or technology over which its applications work, like the **internet is built on top of the protocol TCP/IP**.

Now, not all blockchains use the same protocol - because blockchain is a term that's used to describe a whole category of networks, not one specific network.

There are thousands of blockchain networks out there, and they come with their own protocol.

Few of the blockchains being -
1. [Bitcoin](https://bitcoin.org/en/) - blockchain on which the Bitcoin cryptocurrency runs.
2. [Ethereum](https://ethereum.org/en/) - a global, open-source platform for decentralized applications.
3. [Tezos](https://tezos.com/) - a global open-source platform for assets and applications backed by a global community of validators, researchers, and builders. This is the blockchain on which you are learning to deploy apps on through this course!

#### Why do you even need several blockchain networks when the principle behind them remains the same?
Every network has its pros and cons, use-cases it's suitable for, the algorithm it uses, etc.

Think of it like this, there's a universe where each human has a collection of Cryptobots(robots running on top of blockchain), now the human has a collection because each Cryptobot is specialized to be good at doing a handful of things.
So, each Cryptobot has its suitable use-case, one is good at cooking food for you, the other one is great at fending off enemies for you.

Similarly, there are multiple blockchains, some of them similar to each other, some of them radically different and some of them built for completely different use-cases.

You as a builder can leverage these networks and come up with applications on top of the blockchain, and how to do that will be discussed in the next chapter 🔨

#### How are blockchain apps different?
Applications built on blockchain are quite different from their centralized counterparts.

You can't just go and peak at Facebook's database, it's private. It's a closed ecosystem.

But with blockchain, you can look up any address on the network and see their whole transaction history. It's like a global garden which anybody can visit. But what you can't see is the person to whom the account belongs to, that's a powerul concept. Blockchain has removed the concept of 'personhood', it doesn't need to know who or what is on the either end of the transactions.

#### Should all apps be built on blockchain?
No, not every application needs to be built on top of a blockchain.
Only the applications that benefit from being built on a decentralized, transparent, and tamper-proof environment should be built on a blockchain.

For example, in games when you buy a sword, you don't own that sword. You just own the right to use that sword in the game. What if you could actually own that digital asset? That's what blockhcain can allow, you can literally own a Fortnite skin and then sell it to somebody on the internet for 100XTZ( XTZ is the currency used on the Tezos blockhcain ).

Moreover, even if you're building on top of blockchain - not all your data needs to be on a blockchain. It could be a combination of using a centralized server along with a blockchain, depending on the use-case.

I hope this chapter gave you a better picture of how you can leverage blockchain technology to build applications on top of it. Even if it didn't, don't worry. In the next chapter we'll talk about **smart contracts**, which are the building blocks of a **decentralized application**(DApp).