Game type: Online web-based game
Time demand: Not necessarily a lot of time at one go, but overall it demands a fair bit of attention, be warned.
Cost: Free, although playing without spammy annoying ads and such requires money.
What it is: A browser-based game that puts you in the role of ruler of a province, where you manage various aspects of the province, such as what buildings you build, ratio of military you recruit, what specialties they're trained in, spells and thief ops that are used. The goal is to both grow your lands, and protect and develop them from others, who can attack you for land, plunder, or various other things, not to mention cast spells and use ops against you.
You are not alone in this game, however. Instead, you are part of an entire kingdom of up to 25 provinces total. The kingdom as a whole can go to war, can share information or just chat via the kingdom forum, can aid each other with soldiers, gold, food, or runes (for casting spells), and so on. And really, more than growing you own province, your goal is (usually) to help your kingdom grow and expand and prosper.
How much you enjoy the game will probably depend not only on how much you like it in general, but in the match you get with a kingdom. A very casual player for instance probably wouldn't enjoy being in a very demanding kingdom (and believe me, some are quite demanding, my own is getting a bit annoyingly so), while a hardcore player would be annoyed in a lackadaisical kingdom that just doesn't care, or work together.
Utopia is played in ages, each age lasting a couple months, at which time statistics, high scoring kingdoms and provinces, etc., are placed in the records, and then the new age starts with at least some sorts of changes (usually at least some tweaks to races and/or professions, usually a few to general gameplay as well). The previous age just ended about five days ago, and the new age is still just getting started, so if you may be interested this is a great time to check the game out.