An idiom is (usually) a type of phrase that has a meaning that may not relate to the meanings of its individual words. It is a figure of speech.
If someone's name rings a bell, there is no ringing or bell, but there is a faint memory.
If a certain cold beverage hits the spot on a warm afternoon, there is nothing hit, there is no spot, but it does satisfy you.
As far as I know, every language has idioms.