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Author: davidekete

Intro-to-blockchain-and-ethereum/intro-to-blockchain/README.md

@@ -2,7 +2,13 @@ A blockchain is an append-only ledger shared across many computers (nodes). Unli
 
 On public blockchains (some blockchains are private), identical copies of this ledger are widely replicated, and nodes accept new data only if it satisfies the network’s consensus rules.
 
+## How blockchains work
 
+At a high level, three parts cooperate: an execution layer that deterministically turns transactions into state changes, a consensus mechanism that orders blocks and decides what becomes canonical, and data availability/state so everyone can fetch and verify the data. When these are aligned, immutability is the practical outcome and rewriting history becomes economically prohibitive.
+
+### Consensus mechanism
+
+A consensus mechanism is how the network agrees on the next valid block. For example, **proof-of-stake**, where validators bond capital and can be slashed, and or **proof-of-work**, where miners prove computational effort.
 
 ### Execution Layer