There are two primary ways by which a corporation can raise money: debt and equity.
Debt is what most consumers are most familiar with: a corporation takes out a loan (or issues a bond) which obligates the corporation to repay the amount they borrowed plus some interest to the lender over some period of time. Equity is quite different: equity is when the corporation sells a portion of the company (aka shares, aka stock) in exchange for cash. Both allow the corporation to raise cash quickly in exchange to future obligations to pay (directly in the case of debt, and indirectly for equity in the sense that the new stockholders now own a claim on the future profits of the company).