You are working offline when your computer is not connected to other devices or using an Internet connection. This is opposed to being online, where a device, such as a computer or program, can communicate with other devices or the Internet connection in order to complete a task.
Working offline prevents all information from traveling to or from the computer. This option is more commonly chosen by those using a dial-up connection as it prevents your computer or programs from automatically connecting to the Internet, which can tie up a phone line. You can choose to have your computer or program work offline by selecting the appropriate option.