We use the past perfect simple to talk about what happened before a point in the past. It looks back from a point in the past to further in the past.

I hadn't known the bad news when I spoke to him.

I checked with the supplier and they still hadn't received the contract.

She had already told him before I got a chance to give him my version.

The company has started the year well but was badly hit by the postal strike.

The past perfect simple is often used when we report what people had said/thought/believed.

He told me they had already paid the bill.

He said he believed that John had moved to Italy.

I thought we had already decided on a name for this product.