A Stock Purchase Agreement (SPA) is the principal closing document in a priced equity financing, governing the sale and purchase of newly-issued preferred stock. It contains the financing terms (share count, price, closing date), the company's representations and warranties to investors, the conditions that must be satisfied before closing, the indemnification structure if reps prove untrue, and the closing mechanics. It is the "definitive document" of the priced round, accompanied by the certificate of incorporation amendment, the Investor Rights Agreement, the Voting Agreement, and the Right of First Refusal and Co-Sale Agreement (ROFR/Co-Sale).
The standard content of a Stock Purchase Agreement: