A Series A round is the name typically given to a company's first significant round of venture capital financing. The name refers to the class of preferred stock sold to investors in exchange for their investment. It is usually the first series of stock after the common stock and common stock options issued to company founders, employees, friends and family and angel investors.
Series A Preferred Stock is the first round of stock offered during the seed or early stage round by a portfolio company to the venture capital investor. Series A preferred stock is often convertible into common stock in certain cases such as an IPO or the sale of the company.
Series A rounds are traditionally a critical stage in the funding of new companies. A typical Series A round is in the range of $2 million to $10 million,  purchasing 10% to 30% of the company.  The capital raised during a Series A is usually intended to capitalize the company for 6 months to 2 years as it develops its products, performs initial marketing and branding, hires its initial employees, and otherwise undertakes early stage business operations.