The heavyweight solicitation type. You respond with a written proposal covering approach, qualifications, and price, and the agency evaluates against stated criteria that can include technical merit and past performance, not just cost. RFPs allow negotiation before award.

In a sentence

"Proposals in response to this RFP are due no later than 2:00 pm Eastern." Expect real writing, and expect the evaluation criteria section to tell you exactly what the grader's rubric is.