Dogfooding: eating your own food. Is refer to the practice of using you own product as your main service, being your own customer.
As example, there's a story where every Android (OS) developer where given basic Android phone with low RAM as their main device, they where aiming to decrease the resources the OS required and using the phone by the developers allowed them to experience first hand what low income/cheap phone owners felt IRL, thus allowing them to better focus on improving the product on real pain points experienced by themselves