There is a history of states for syncing & auditing purposes, but only the current state of the ledger is referenced when appending/voting on new transactions.
If you are syncing from a historic point, say if you were offline, then your node would request the state actions you are missing, and action them to get to the same state as everyone else.
So there is a chain of history? Which is it, I'm confused?
Ok, so assuming there is a chain, and I am a syncing node just joining the network for the first time AND I am presented with two different chain histories, how do I know which one to pick?
There is a ledger, not a single chain. The ledger is of n channels, which contain past transactions for that channel arranged as a tree.
IF you were to join and be presented with a 2 ledgers to sync from the genesis transaction, only one would be valid. That would be the ledger where the first transactions are voted for by the bootstrap nodes.
So you can't have 2 ledgers to start with, unless all operators of the bootstrap nodes have signed the first transactions in both (which they wont)