The term has specific meaning with respect to computer technology and telecommunications.

To be considered on-line, a device must be at least one of:

• Under the direct control of another device.
• Available for immediate use on demand by the system without human intervention
• Under the direct control of the system with which it is associated.
• Connected to a system, and is in operation
• Functional and ready for the service

Online more commonly means connected to the Internet. Online advertising is done exclusively on the web or through e-mail.