NetBoot is a small MultiBoot-compliant operating system, and example of OSKit use, that provides one service: fast booting of other MultiBoot-compliant operating systems across the network while itself remaining resident in order to regain control after the target OS exits. This avoids going back to the BIOS to boot the next kernel and allows a reboot cycle that is often an order of magnitude faster than normal.
When NetBoot is booted it prompts for the name of an OS to fetch and boot. The booted OS is passed a special command line flag indicating a return address that it can use to return control back to NetBoot upon exiting. Therefore NetBoot could be thought of as a crude batch-processing operating system.
NetBoot is intended to be used as a kernel development tool, not as a mechanism for implementing diskless workstations, although it can conceivably be used either way.
Note: the netboot described here is not to be confused with the FreeBSD netboot EPROM code of the same name. They share some code but perform different functions.