A Letter of Inquiry (LoI) (aka Proposal Letter) is a short expression of your project in letter format. It is often associated with the cover letter and they both have many similarities. However, an LoI is sent to a donor before a proposal, while a cover letter is always sent with a proposal.
The example below is only a sample template to give an idea of how to format your letter of inquiry for a successful donation and what information should be included.