An idiom is defined as - a group of words whose meaning is different from the meanings of the individual words.
Idiom:
give (someone) the low-down (on someone or something)
Meaning:
to tell someone the full story or details about someone or something
Example:
I gave my friend the low-down on our plans for the weekend.
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.