Common shares represent ownership in a company and are a fundamental way for individuals to invest in businesses. When someone buys common shares, they gain a claim on the company's assets and earnings, which can lead to potential profits through dividends and capital appreciation. Holders of common shares typically have voting rights, allowing them to participate in important company decisions, such as electing the board of directors. However, common shareholders are last in line to receive any remaining assets if the company goes bankrupt, making their investment riskier compared to preferred shares.