Part 9/19:
The blockchain is described as a linked chain of blocks, each referencing the hash of its predecessor, forming an immutable sequence anchored to the Genesis block. Nodes (computers managing Bitcoin) can independently verify the integrity of the chain by recalculating hashes from the Genesis block up to the latest, ensuring the chain's authenticity. This process allows any node to join or leave the network, sync with the latest state, and trust the historical record without centralized authority.