This builds on cy.intercept, so it is also something you run on a local project rather than in the editor here. The technique is standard on real Cypress teams, and interviewers ask about its trade-off often.
Your product manager asks a fair question: "What does the app show when the server is down?"
You want to test it. But how? You cannot break the real server just to run a test.
You can make Cypress answer the request for you. This is called stubbing: your test gives a fake answer instead of letting the request reach the real server.