The document discusses lexical bundles, which are frequently occurring multi-word expressions in a given register or genre. Lexical bundles are not complete grammatical structures or idioms, but rather bridge phrases. They serve important functions in constructing discourse and indicating success within discourse communities. The document provides examples of lexical bundles from conversation and academic prose and categorizes them based on structural patterns and functional classification. It also discusses the importance of teaching lexical bundles to language learners.