Cheng Yu are Chinese idioms, usually four characters long, often associated with a story, either folk or historical. And there are THOUSANDS of them. I think I'll have learned over 100 from my texts this semester alone, along with a bunch on the side.
Today's is: Qi2 Lv2 Zhao3 Ma3 (the lv is a lu with an oomlaut over the u)
Ride donkey, search for horse.
It usually means to be with one girlfriend while on the lookout for another.