Layer 1: The Base Blockchain

Layer 1 just means the base blockchain itself - the network with its own validators, its own consensus rules, and its own native token. Bitcoin is a Layer 1. Ethereum is a Layer 1. So are Solana, Avalanche, and dozens of others.

When people call something 'a blockchain' with no other qualifier, they usually mean a Layer 1: a self-contained system that doesn't depend on any other chain to function.

A Layer 1 bundles together everything a blockchain needs to do on its own: it orders and executes transactions, reaches consensus on the result, publishes the underlying data so anyone can check it, and settles - makes the outcome final and irreversible.

Because one network handles all four jobs itself, a transaction confirmed on a Layer 1 doesn't need any other chain to vouch for it. That self-sufficiency is exactly what later lets other systems borrow its security, which is where Layer 2s come in.

Every Layer 1 makes choices. More validators and stricter hardware-independence tend to mean stronger decentralization and security - but also a lower ceiling on how many transactions the network can process per second.

A chain can loosen those constraints to go faster, but it's spending some decentralization or security to get there. There's no free lunch at the base layer - which is exactly the tension the next lesson names directly.