What Does Online Mean?
Online, in a generic sense, refers to when an electronic device is on and connected to other devices, such as another computer, a network or a device such as a printer. More recently, the term online has come to mean connected to the Internet. In this case, either a person may be online when he or she is using the Internet, or the computer itself may be said to online when it has established an Internet connection.
Techopedia Explains Online
Devices such as printers and scanners are considered to be online when they are running and connected to a computer system. In regards to connection to the Internet or other network, computers would technically be considered to be online when they are connected to a network (such an an intranet), but most people use the term to refer to Internet connection only. When a computer or device is not online, it's said to be offline.
Online can also be used as an adjective to describe activity performed while on the Internet, such as online shopping.