This lesson is about idioms. Idioms? An idiom is an expression that cannot be understood from the meanings of its separate words but has a meaning of its own. For example: a person can be a big cheese. Do you know what is meant?
This expression has nothing to do with a person's appearance. It has a figurative meaning and expresses that someone is an important person in an organization.
A big cheese can be used in various ways, here are some examples: