Trivia games are amongst the most popular games of all times. Its popular among all age groups. Even before internet took over our world, trivia games were played and shared with fun and enthusiasm via books and TV. The appeal of this class of game is that trivia not only entertains and challenges, but it teaches at the same time. According to definition, trivia judges grammar, rhetoric and logic, three skills hence the name trivia. The game is really popular because of the fact it forces our mind to think in an non-conventional way. Some problems which might seem to have typical solution have really simple hidden answer in the question itself. It's fun sometimes to know how tricky and yet elegantly simple the quiz is. These kind of quizzes fall into trivia games.
When internet came along, it did no harm to the popularity of trivia games, it increased like a stampede instead. Sharing things online is a piece of cake and some really cool and tricky quizzes got spread virally. This aids to increasing popularity of trivia games online.
Some websites offer a huge collection of trivia games. Generally online trivia games follow todo different scoring paradigm : points & badges. You earn points as you go on clearing the game. It helps to compare score against others participating in the game and hence gives this whole thing a sense of competition. Badges are awarded when you reach a set threshold score say "Genius badge" for scoring 85 out of 100 and so on. Scoring helps in keep the challenging and competitive spirit and keeps the player pushing.
All in all, trivia games are really cool for fun and some IQ exercise.