A term sheet is a non-binding document that outlines the basic terms of a proposed investment in a company, including valuation, investment amount, equity stakes, voting rights, liquidation preferences, and other key protections for investors. It serves to establish agreement on important deal points before incurring the costs of drafting binding legal documents, and helps prevent misunderstandings between the investing and founding parties. Key clauses in a term sheet address issues like anti-dilution protection, liquidation preferences, option pools, affirmative consent rights, and exit rights for investors.