Why don't bitcoin escrow transactions require a third party? I've read this article: What are &quot;routine escrow mechanisms&quot;?

But I don't understand the bitcoin escrow system.

Can anyone explain me how this escrow system doesn't need a third party ?

Edit : How is solving problems the third party solve in online exchange ?
Bitcoin escrow schemes that don't require a third party typically don't require a third party because that is one of their design requirements. It's obviously much easier to design an escrow system that does require a third party, so typically you would only design one that didn't if you had no choice.