This document discusses collocations, fixed expressions, and idioms. It defines each term and provides examples. Collocations are words that commonly go together, like "fast train" or "fast food". Fixed expressions are phrases with secret code-like meanings, such as "don't teach your grandmother to suck eggs". Idioms are phrases with meanings different from the individual words, like "don't give me any of your lip". The document aims to explain why learning collocations is important for being natural, expressing oneself richly, and making language easier to remember.