A "stock split" is a split of existing shares of stock into a different number of shares of stock. For example, if a company has 2,000,000 shares outstanding, and undertakes a 2 for 1 stock split, it will have 4,000,000 shares outstanding after the stock split. A reverse stock split results in less shares being outstanding. For example, if a company has 6,000,000 shares outstanding and does a 1 for 2 reverse stock split, the company will end up with 3,000,000 shares outstanding after the stock split.