Ethereum is a decentralized blockchain platform where developers can develop and deploy smart contracts and decentralized apps (dApps). It has its cryptocurrency, Ether (ETH), which is used for transactions and encourages members to protect the network through mining or staking.

Ethereum nodes are individual computers that participate in the Ethereum network. They are essential for maintaining the network's decentralization while also ensuring its security and integrity. Ethereum nodes are classified into many different groups, which include:

Full Node

• All nodes hold entire blockchain data, but it is deleted regularly, therefore, not all state data is stored back at its origin.

• Contributing to block validation by validating all blocks and states.

• Full nodes can derive all states, except very ancient states, which are rebuilt by queries to archive nodes.

• Serves the network and delivers data upon request.

Light Node

• It simply stores the block header and is dependent on the entire node.

• For low-capacity devices that cannot store large amounts of data.

• Light nodes do not participate in consensus and cannot be miners or validators. However, they may access the Ethereum blockchain with the same capabilities as full nodes.

Archive Node

• The entire node archives past data and requires terabytes of disc space.

Ethereum accounts may send and receive transactions using their ether (ETH) balance. Ethereum has two types of accounts: externally owned accounts (EOAs) and contract accounts.

For example: you have a personal bank account, which is similar to an externally owned account (EOA) on Ethereum. Your private key gives you power to this account (similar to a bank account PIN). You may transfer and receive money from your bank account in the same way that an EOA can send and receive Ether (ETH) in Ethereum. Assume you have a vending machine that distributes products when you input coins. This vending machine worked similarly to an Ethereum contract account. The vending machine follows a specified set of rules (smart contract code) when you enter coins (send Ether). It can keep the money until you pick an item, after which it will distribute the item based on its code. The vending machine does not have a private key and instead runs according to its programming, similar to a contract account. In this example, your bank account is an EOA, and the vending machine is a contract account on Ethereum.

A smart contract is a self-executing contract in which the buyer and seller's agreement is directly written into lines of code. For example: A farmer wants to sell vegetables to restaurants nearby. They use a smart contract: he defines the produce and pricing, and the restaurants agree and pay into it. He delivers, modifies the contract, and gets paid automatically. Disputes can be settled fairly. This promotes trust and efficiency in transactions.

Decentralized apps (DApps) are those that operate on a decentralized network of computers, such as a blockchain. Unlike traditional programs that rely on a central server, DApps function using blockchain technology's distributed nature.

The Ethereum Virtual Machine (EVM) works similarly to a computer running on the Ethereum network. It uses smart contracts, which are programs that may complete tasks automatically when particular conditions are satisfied. The EVM ensures that these contracts are executed accurately and securely, minimizing the need for a central authority.

Gas is like fuel for Ethereum transactions. Every task or transaction takes a specific amount of petrol to execute.

Gas Price is the amount you are willing to pay for each unit of gas. It's similar to fixing the price of petrol per gallon.

The gas limit is the maximum quantity of gas you are willing to expend during a transaction. It's similar to limiting the amount of money you're willing to spend on gasoline for a vacation. If the actual gas consumed exceeds the limit, the transaction fails, and any remaining gas is returned.

A decentralized autonomous organization (DAO) is an organization represented by rules stored in a transparent computer program, managed by its members, and not impacted by a central authority. A DAO's financial transactions and regulations are stored on a blockchain, usually Ethereum. DAOs are run by programming code rather than individuals, and they carry out acts depending on member votes. They are commonly utilized for decentralized governance and financial management without the requirement for a central authority.

Important terms to know:

The DAO Attack: an attack that exploited a weakness in a smart contract and stole cash. It caused a split in the Ethereum blockchain to undo the theft.

• Hard Fork: A significant modification to blockchain technology that validates previously invalid transactions, forcing all nodes to update.

• Soft Fork: A backward-compatible protocol update, allowing non-upgraded nodes to continue communicating with the network.

• Initial Coin Offering (ICO): A fundraising strategy in which new cryptocurrencies are sold to investors in return for existing cryptocurrencies.

• Ethereum 2.0 (Serenity): An update to Ethereum designed to increase scalability and security by introducing a new consensus process and sharding.

• Sharding is a strategy for increasing blockchain scalability by breaking the network into smaller, more controllable pieces.

• Altcoins are cryptocurrencies that differ from Bitcoin in terms of features and use cases. Examples include Ethereum, Litecoin, and Ripple.