Eerily life-like virtual people get jobs, spouses, friends, home furnishings, and children. They have hobbies, wants, fears, aspirations, and drama within their social circles. It's so creepy how real they can become.
You the player are in control of everything they do and can make each sim's life perfect or a living hell - and everthing in between. Eventually Sims get old and die. Hopefully they've raised good children so their family tree can continue growing once their gone - if that's the way you'd like to play. It's totally up to you.
"Delete the family and make a new one, it's just a game."
boy: idiot! sims two DUH!
girl: for how long?
boy: about a week!
boy: cause its friggin adictive!
girl thinking 3 hours later: oh shoot!!!! its 1:00 am what am i doing i have to get off right after i redecorate their house
girl thinking 1 hour later: damn, i wish this game would save faster!