It doesn't, it verifies who it came from. Someone else mentioned Maersk above for supply chains, but a blockchain allows both Maersk and I to verify independently, without trusting each other, that a third party has made a change. If the third party says Maersk has it, and Maersk say the third party have it, the blockchain will have a record of it if Maersk accepted it, and I can independently verify that.

Unfortunately this isn't actually a property of a blockchain, this is a property of a ledger. I'm still trusting Maersk in this situation, because if I don't, what do I do, fork the blockchain and pretend that Maersk has the item?