Wikipedia calls it rice congee. I call it xifan (稀饭). You don't usually find them in Chinese restaurants in the United States. It's super easy to make:
¾ cup long grain white rice
7½ cups of cold water
(My rice measuring cup is ¾ cup big. So for me it's 1 cup rice and 10 cups water.)
Put on high heat in a stockpot for 10 minutes or till the water boils. Reduce the heat to medium-high (8 on my dial) and let it simmer for 20 minutes. Stir every so often (especially during the minutes before the water boils) to prevent the rice from sticking to the bottom of the pot and get burned.
This is what I would make when I don't want to have a big dinner:
"What do you want for dinner?"
"We had a big lunch. I'm not hungry. Let's have xifan."
It goes well with any kind of seasoning. When I'm lazy, I'll just have xifan with pickled cucumber from the jar.
But I do remember having xifan with crushed roasted sesame seeds, salt, and sugar as a little boy.