What is the difference between an RFP, RFQ, and RFI?

A Request for Proposal, or RFP, solicits detailed proposals from vendors describing their approach, methodology, team, timeline, and price for a defined scope, used when the solution requires evaluation of technical approach, not just price. A Request for Quotation, or RFQ, solicits price quotes for a well-defined, standardized product or service where the buyer knows exactly what they want and selection is primarily based on cost.