A good distraction... if you're 10 years old.
The premise of the very minimal story is that you, a human character that can be either male or female, have moved away from home and taken up residence in the town of Animal Crossing (though you can name the town whatever you want). You mortgage your house, which is basically the size of a box with a bed and a radio, from the cute racoon shopowner, Tom Nook. Don't let his cuddliness fool you, though. This little creature will be the source of much of your pain in Animal Crossing, due to him being more greedy than a Mafia loanshark. Seriously, this guy is evil. Many a time have I wished to bash his little racoon face in with a shovel... sorry about that. Moving on...
So the main goal of the game is to upgrade your pitiful shack into a sprawling, 2-story manor. This is done through paying off your mortgage to Nook by earning bells, the game's currency. You can take a part-time job at Nook's store, which upgrades throughout the game as well, or take time to go fishing or bug-catching. As you pay off your enormous debt, your house is automatically upgraded, earning a basement and a second floor. This is probably the part of the game that will keep you motivated for the first month or so, as the house is infinitely customizable. I personally used the second floor as an NES shrine, as you can unlock classic NES games to play in your house. This is actually a pretty cool feature, as there's some pretty cool games like Excitebike and Clu Clu Land. There's some other diversions, like designing your own clothes and washing cars, but they're not enough to keep you occupied.
However, the same reason you'll probably keep playing the game is the same reason you'll eventually become incredibly bored with Animal Crossing. The sheer tediousness of the game is mind-boggling. Let's outline a typical day in AC:
1: Go see Nook for a job.
2: Go talk to an annoying animal to recieve a fetch-quest!
3: Fish.
4: Catch bugs.
5: Design clothes.
6: Fall asleep with your Gamecube controller still in your hands.
It's not that the mechanics of the game are broken in any way, it's just that there's not a lot of them. After playing for a couple months, I hadn't played this game in years until recently. I picked it up just to see what it was like today, and honestly, for a game that's supposedly so real-time and realistic, nothing much had changed, besides my house basically going to hell with cockroaches.
If you're looking for a game to introduce a child to gaming, Animal Crossing is a pretty good choice. Just don't expect it to last for more than a couple months.