A PXE server (Preboot Execution Environment server) is a network service that allows computers to boot up and load an operating system over a network instead of using local storage devices. This is particularly useful for deploying operating systems to multiple machines simultaneously, such as in large organizations or data centers. When a computer is powered on, it can send a request to the PXE server to obtain the necessary files to start the boot process. This method simplifies system management and reduces the need for physical media like USB drives or CDs, making it easier to maintain and update systems across a network.