To “boot” is to start up a computer system, so to reboot is to restart the system. Typically, this doesn’t involve actually turning off the power to the computer, but rather closing down and restarting the operating system, which clears out all the RAM, caches, and other storage spaces, and returns the computer and operating system to their default state. Rebooting will also quit any programs that might be running, so any data contained in them will be lost if it isn’t saved to hard drive or other storage medium.
