Cash management involves managing a firm's cash flows, balances, and converting surpluses and deficits. It aims to maintain enough cash for transactions while maximizing returns on excess cash. The Miller-Orr model sets upper and lower control limits for cash balances and a return point to buy or sell securities if balances exceed the limits. Firms can accelerate cash collections through decentralized collection centers and lockboxes, and manage disbursements by controlling payment float. Surplus cash can be invested in safe, liquid securities like treasury bills, commercial paper, and certificates of deposit.