"Online" and "offline" are terms used in telecommunications. If a computer or a user is connected to the Internet, it is said to be "online".[1] A website, for example, is online, because it is on the Internet.
If something is not online, it is said to be "offline". If a system is offline, it is in a disconnected state.
Online can also mean that something is set up correctly and ready to what it is supposed to do. For example: