Today is a day called Tet, which is like New Year's Day but lunar, meaning it's based on the moon.
It is a special day, full of traditions; the people eat treats and wear all new underclothes.
It is believed that the way you behave on Tet determines your year.
Along these lines, there are things people can't do, too, like sweep or splash water, and they must smile all day long.
The coolest thing of all, though, is that Tet is everyone's birthday. What does that mean? Well, the narrator is ten years old but she is considered one year older on Tet, instead of on the anniversary of the day she was born. We can tell she might be a girl because she says that she is learning to embroider (although ain't no shame in the male embroidery game), in addition to learning fractions and taking care of a papaya tree.
In this culture, men are supposed to bring luck, so her brother was asked to rise early to bless the house with his feet (to bring the family luck), which makes the narrator mad so she wakes up early to touch her toe to the floor first.