Idioms : A phrase which has a meaning that is commonly understood by speakers of the language, but whose meaning is often different from the normal meaning of the words is called an idiom.
What is your favorite Idiom?
Here are some of mine:
All hat, no cattle
You can lead a horse to water, but you can't make it drink!
Sleep like a log
Better the devil you know than the devil you don't.
Singing from the same hymn sheet.