Here's why:
* Literal Meaning Doesn't Apply: Idioms are phrases whose meaning is not the sum of their individual words. For example, "kick the bucket" doesn't literally mean to kick a bucket.
* Figurative Language: Idioms use figurative language to convey a meaning that is often metaphorical or symbolic.
* Cultural Context: Idioms often have specific meanings within a particular culture or language. What might be a common idiom in one culture might not be understood in another.
Examples of idioms:
* "Break a leg" - This means "Good luck!"
* "Spill the beans" - This means "To reveal a secret."
* "Hit the road" - This means "To leave."
* "Once in a blue moon" - This means "Rarely."
Because idioms rely on figurative meaning, they can be confusing for people learning a new language or for those unfamiliar with the culture where the idiom originated.