Idioms are expressions of words or phrases whose meaning cannot be explained directly from the meaning of individual words that make it up.
Example :
1) Under someone's wing
If you go through above example word by word, then the literal meaning of it would be like you're in the wing of someone or you're sitting in the wing of some bird while this is absolutely wrong. The meaning of this idiom is " to be under someone's protection ".
Learn about more Idioms and Phrases in the following quiz.