Working capital is the funds required for a company's day-to-day operations and is calculated as current assets minus current liabilities. It covers costs associated with inventory, accounts receivable, and cash needed for ongoing business activities. The amount of working capital needed depends on factors like the nature of the business, production cycle length, seasonal fluctuations, and company size. Companies must determine the optimal working capital policy that balances risk and profitability, such as aggressive policies with low cash levels or more conservative approaches.