if, in some way, there are 2 nodes whose ledgers have conflicting transaction histories, how is it selected which model all of the customers should go by?
Every node decides for itself. Every node makes these types of selections independently. No node trusts every other node to make these selections for it.
Every node independently examines all the information in all the choice chains it creates because it receives information, together with conflicting information. Every node independently calculates the quantity of “work” represented by every chain and selects the chain with the very best quantity of labor as its energetic chain. This resolution is re-examined each time the node receives information that alters the quantity of labor represented in any of the chains it is aware of about.
As a result of all Bitcoin nodes observe the identical guidelines for this, all of them independently choose the identical chain. They naturally obtain consensus with none specific collaboration, voting or central path.
Most chains have a standard ancestry and solely the final block or so differ. Which means that maintaining observe of a number of chains could be achieved comparatively effectively with out duplicating the frequent portion.
The measure named “Work” relies on an estimate of the common variety of hashing makes an attempt that will be wanted to search out an association of information that produces a block with a hash lower than the goal relevant on the related block top.
Footnote on terminology
Though many individuals describe the Bitcoin blockchain as a ledger, that’s deceptive. Accounting ledgers have accounts and balances. The Bitcoin blockchain is a straightforward transaction journal not a ledger. It incorporates no accounts and no specific balances.