Bitcoin introduced the world to a secure, decentralized way to store and transfer value, much like digital gold. Ethereum takes that core idea and expands on it. If Bitcoin is like a simple calculator that does one thing very well, Ethereum is like a smartphone. It’s a platform where developers can build and run all sorts of applications.

At its heart, Ethereum is a global, decentralized computer. Instead of a single company like Google or Amazon running the servers, the network is run by thousands of computers worldwide. This means applications built on Ethereum are open, censorship-resistant, and not controlled by any single entity.

The key innovation that makes this possible is the smart contract. A smart contract is just a program stored on the blockchain that runs when predetermined conditions are met. Think of it as a digital vending machine. You put in a coin (cryptocurrency), select an item, and the machine automatically dispenses your snack and change. There's no cashier needed; the rules are baked into the machine itself. Smart contracts do the same for digital agreements, automatically enforcing the terms without needing a lawyer, bank, or other intermediary.

How does this global computer actually run all these smart contracts? The answer is the Ethereum Virtual Machine, or EVM. The EVM is the environment where all smart contracts and Ethereum applications live and execute. It’s the engine of the Ethereum network.

Every computer (or node) participating in the Ethereum network runs a copy of the EVM. This is what keeps the system decentralized. When someone interacts with a smart contract, every node on the network processes that transaction through its EVM. This collective computation ensures that everyone agrees on the outcome, making the system transparent and secure.

Running computations across thousands of computers isn't free. To prevent spam and to compensate the people running the network, Ethereum uses a concept called gas.

Gas is the fee required to conduct a transaction or execute a contract on the Ethereum blockchain. It's the fuel for the EVM. Every operation a smart contract performs, from simple addition to storing data, has a specific gas cost.

These fees are paid in Ethereum's native cryptocurrency, Ether (ETH). When you send a transaction, you set a gas limit and a gas price. The gas price is how much you're willing to pay per unit of gas. The people running the network (validators) prioritize transactions with higher gas prices, especially when the network is busy. This system ensures that the network's computational resources are used efficiently.

Let's test your understanding of these core concepts.