Requests for admission are a list of questions which are similar in some respects to interrogatories, but different in form and purpose.
Notably, under Rule 36(a)(3),[1] requests for admission are automatically deemed admitted in U.S. federal courts if the opponent fails to timely respond or object.
While evidence introduced at trial can be rebutted, admissions which are on record must be taken as true unless the judge permits them to be withdrawn or amended.
Thus, requests for admission can obviate presentation of some evidence and make the actual trial shorter and more efficient.
Also, Federal Rules of Civil Procedure have placed 25 questions per party limitations on the use of interrogatories, but there is no numerical limit in FRCP on the requests for admission (unless specified differently in Local Rules of the state, which most states do have).