This is the combination of the Requests for Admission, Requests for Production, and General Form Interrogatories, providing the most cost-effective discovery. The purpose of discovery is to find out what the other sides knows or will claim, so that at trial you can be prepared with your counter-evidence and are not taken by surprise.
The requests for admission ask them to admit the things you want to prove. They admit or deny them. Then the general form interrogatories [questions] ask about several things, most importantly #17.1, asking for the facts, witnesses and evidence they have to support any denial of a request for admission: what facts do they have to support their denial, who knows about it, and what evidence do that have to support their denial. The request for production requires that evidence they describer to be produced, plus other things like their ledger of account, all communications between you, contract papers, repair receipts, and other things that affect your case. By the time we get that information, the landlords case is laid open, exposing all the weaknesses.