Online means connected to the internet or available through the internet. When you're online, your computer, tablet, or phone is connected to a vast network that links millions of devices around the world, letting you visit websites, send messages, play games with distant friends, or watch videos.

The word contrasts with offline, which means not connected to the internet. You might read a book offline, play a board game offline, or work on a drawing offline. Some activities require being online: you can't video chat with your cousin across the country unless you're both online. But many things work just fine offline, and some people deliberately go offline to focus better or enjoy time away from screens.

People also use online to describe where something exists or happens. Online shopping means buying things through websites instead of going to physical stores. An online class takes place over the internet rather than in a school building. An online friend is someone you know through the internet but might never have met in person.

The internet began in the 1960s as a way for university computers to share information, but the World Wide Web (created in 1989) made going online accessible to regular people. Today, being online is how billions of people learn, communicate, work, and play.