A cybernaut is a person who uses the Internet to explore and communicate. It's becoming more and more rare to meet anyone who isn't a cybernaut these days.
Cybernauts tend to spend time online interacting socially in forums and through social media. At one time, cybernauts were thought of as adventurous explorers of a new realm — the Internet — but increasingly there are few people who can't call themselves cybernauts. The earliest use of the word referred to users of any computer technology, especially virtual reality, borrowing from astronaut and adding the prefix cyber-, used for electronic communication and computer-related words.