An idiom is a type of phrase or expression that has a meaning that can't be deciphered by defining the individual words.
Idiom:
steal the spotlight
Meaning:
to do so well in a performance that you get most of the attention
Example:
The singer always steals the spotlight when she sings.
List of common idioms, their meanings and examples of their usage in sentences
An expression in the usage of a language that is peculiar to itself either in having a meaning that cannot be derived from the conjoined meanings of its elements or in its grammatically atypical use of words.