Idioms are phrases that cannot be translated word-by-word but have meaning beyond their literal dictionary definitions. They are one of the hardest challenges for someone learning a language.
However, if you want to communicate with native speakers, knowing at least the most common idiomatic expressions is important. You’ll find that native speakers use them very, very frequently.
How frequently are idioms used in English? Trying to get solid facts, I came across the following two citations on
Nada’s ESL Island, a tropical-looking, informative Web site established by Nada Salem Abisamra of George Washington University: