Question about the sims
Well, it is a game, released by Electronic Arts. It is now on it's 3rd incarnation as Sims3. I can only really speak for Sims2 and Sims3.
Both games are really the same at heart though - you install the game on your computer (it is a single player game) and you build a world/hood and put buildings in it (houses, shops, parks, businesses) and you make a sim and get that sim to live in your world.
Sims have things they want and need and you try and give the sim the things they want to make them happy (that is how I play anyway). Sims need to be fed and kept entertained - they can breed and produce little sims, and eventually you get a whole world full of sims that you know. It is like being a god. Sort of.
So what do we do? We make things (windows, doors, sofas, etc) or make clothes (jackets, trousers, hats, etc) or make things for sims appearance (hairstyles, makeup and stuff) - and some of us make mods and hacks for the game to modify the original way the code was written.
On this site, BO is our master modder.
Using the game to tell stories:
Look at some of these legacy stories on livejournal/blogger/dreamwidth ETC.
Remaking the game to your own vision:
The complete medieval hoods and sci-fi hoods people make. The houses and furniture that people make for their games. Modding the game code to make things the way you want them to be.
Using the game engine to make films:
There is a thriving community of film making simmers - I remain in awe of most of them.
Some people "play" by building and decorating houses and neighbourhoods. You can build houses from scratch you see - place the walls and floors and everything, design it however you want. Great for wannabe architects!
Others like creating characters (called "sims) and customizing their look - the game lets you edit their faces to look however you want, so you can make fairly accurate versions of yourself, your friends, fave celebrities, or just a completely made up character.
Some people like making objects for the game, or clothes, wallpaper, windows - you name it. Pretty much everything can be customized.
Some just like playing "normally" - putting characters in a house and giving them virtual lives. It's not just about satisfying their "wants" and "needs". These creatures are entertaining to watch. They are very funny and oddly endearing. They have personalities (which you set when you make them) and act accordingly. You can give 'em romances, families, jobs... make 'em good or bad... nurture 'em or kill 'em. It's all up to you. There's no winning or losing in Sims. It's a very open-ended game.
Then there are those who like using it to take pictures and make videos. You can direct the characters to do what you want, so making videos is fairly easy (especially with the help of mods/hacks) and lots of fun.
I'd say the fact that it's SO versatile and open-ended is what makes it so popular. It attracts a lot of different people who use it differently. And when you get tired of one aspect, there are plenty more to explore. There's no end to the game. No puzzle to solve, monsters to kill, story to resolve. You don't get to level 27, beat the monster, then stick it on a shelf and never play again. This gives the game lots of staying power which keeps folks playing for years.
And even when I'm not playing, I'm still busy with my sims game as a modder.
I'm either playing Sims, or working on my Sims story, or trying to build suitable houses for my sims, or trying to add new features to the game code to give my sims more or better options. Or I can be found on several Sims-oriented forums, trying to help people with sims-related problems and issues, commenting on people's sims-creations, reading their sims-stories, etc... And when I'm not behind the keyboard, I'm asleep, and probably dreaming about certain aspects of my Sims game. In a sense, I'm simming 24 hours a day now.
I've been playing 12 years now, and don't see myself stopping anytime soon. And I haven't gone through all the features in all 3 versions (although I have played all of them).
I've learnt all sorts of new skills and interests through the sims - design, architecture, art, modding, photoshop, graphics, history. And the politics and drama of forums and real life. (Please tell me that governments aren't just forum wars, I don't think!). I've discovered life-long friends and bitter enemies within the community - not bad for a game about little people.