A letter of intent expresses the parties' shared intent to transact and outlines the key commercial terms, but it's not legally binding (with limited exceptions like exclusivity or confidentiality clauses). LOIs are common in three contexts: large enterprise sales (the 'paper LOI' before procurement), partnership negotiations, and M&A.
In fundraising, the term sheet plays the role an LOI plays in M&A. Founders sometimes use LOIs from large customers as traction proof in fundraising decks; they're useful but discounted because they aren't binding revenue.