A computer port is used to:

A computer port serves as a physical or virtual interface point that allows the computer to communicate with peripheral devices such as printers, keyboards, mice, and external storage. Ports provide the necessary connection points for data transfer between the computer's internal systems and external hardware components. The other options are incorrect because downloading files requires network connectivity not just a port, communicating with all hard drives uses internal interfaces like SATA/IDE not ports, and connecting computers together typically requires network cards or crossover cables.