There has been a subtle, but significant, shift from describing systems as online to digital. I think this is an important distinction in the way we use and think about technology.
The term “online” was originally coined to indicate a state of connectivity. Primarily this was whether the device in question was connected to a computer or network. This was in an era when network connectivity wasn’t assumed. Conversely “offline” indicated a disconnected state. See en.wikipedia.org/wiki/Online_and_offline
Remember America OnLine? It’s now really only referred to as AOL.com.
In my view, nowadays, online pretty much equals web.
This is where the digital term takes over from online. It takes an ecosystem view of channels & interactions that is much, much wider than purely web.
This includes mobile web, mobile apps, tablets, social media, ecommerce, portals, web services, kiosks, touch screens, M2M, TVs, advertising billboards, and pretty much anything that has a screen.
Half of all Facebook traffic is now via mobile devices. “Online” just doesn’t seem to fit that model any longer.
PS. I also really like it when you put a hyphen in on-line. Makes it look old school.