RFP ( Request For Proposal ) and RFI (Request For Information) are often used by companies to get certain information from vendors about their ability to accomplish a particular task. RPF or request for proposal is usually demanded from vendors by companies to know their nature of service, the capability of a potential vendor, plus the costs for each service rendered.
RPF looks more structured compared to RFI in that potential vendors can still be subjected to further tests so that the best person will be chosen for the job. For example, companies may decide to ask potential vendors about how they intend to solve their problems, and they intend to manage the cost of the project.
On the other hand, RFI or request for information is a particular way of requesting all the information you need from potential vendors. This usually includes their experience, rates, and other information that will make them qualify for the job. Financial information or cost of service might not be included.