How does Stellar work? At the lowest level, Stellar is a system for tracking ownership. Like accountants have for centuries, it uses a ledger to do so, but Stellar’s innovation is that there is no actual accountant. Instead there’s a network of independent computers each checking and rechecking the work of the others. Stellar is a system without a central authority—meaning no one can stop the network or secretly adjust the numbers to his liking—yet even without a central authority the ledgers are verified and updated, every five seconds.
A unique algorithm, called the Stellar Consensus Protocol (SCP), keeps everything in sync. There are many ways to get agreement across a decentralized system—Bitcoin’s visionary proof-of-work method was the first and is still the most famous. But, like many first drafts, proof-of-work left room for improvement. SCP strives to be better by being configurable, fast, and highly energy efficient. If you’re interested in the deep details, you can read the peer-reviewed paper, published by SOSP, the oldest and most prestigious systems conference, for complete technical details.
For every account holder, Stellar’s ledger stores two important things: what they own (account balances, like “100 pesos tokens” or “5000 lumens”) and what they want to do with what they own (operations, like “sell 10 dollar tokens for 50 lumens” or “send 100 peso tokens to such-and-such account”.) Every five seconds, all the balances and all the operations are broadcast to the entire network and resolved.
The computers that run the core Stellar software and therefore publish and check the ledger are called nodes. So, when you send someone a euro token on a Stellar-built app, the nodes check that the correct balances were debited and credited, and each node makes sure every other node sees and agrees to the transaction. The current Stellar network is verified by hundreds of nodes across the globe; the nodes and how they communicate is public information, and anyone can install the Stellar software and join the consensus process. This is different than how accounting works at, say, a bank, where a single corporation unilaterally decides what happens, more or less in secret.
Right above this core layer sits a powerful API so that to build on Stellar you don’t have to understand the particulars of distributed consensus. Simple, well-documented functions allow you to move new digital money using models that you’re used to. It’s very easy to trade tokens between accounts, make markets, and issue assets.