Venture debt is a loan made to a venture-backed company, usually structured as a multi-year term loan with monthly amortization, an interest rate of 8 to 12%, and warrants for equity. It's most often used to extend runway between equity rounds, fund equipment, or finance accounts receivable.
Lenders underwrite primarily on the strength of the company's recent equity round, the quality of its existing investors, and the burn rate. Venture debt is cheaper than equity in dilution terms but adds fixed obligations that can compound problems if the next round slips.