Cloud computing refers to storing and accessing data and programs over the Internet instead of a computer's hard drive. It provides advantages such as cost efficiency since users only pay for resources used, elasticity in capacity as users can increase storage and computing power as needed, reliability through redundancies to prevent data loss, and device/location independence allowing access from any Internet-connected device. Key benefits include pay-as-you-go pricing, scalability, robust security protections, and the ability to access files and run programs from any location.