The document discusses colloquialisms, idioms, and slang. It notes that while ESL students can master formal English, they often struggle with informal everyday expressions. ESL classes do not adequately prepare students for the slang, idioms, and colloquialisms commonly used in casual conversation. The document provides examples of idioms like "drop the ball" and "get your feet wet" and explains what colloquialisms are. It recommends that students, especially international students, keep a vocabulary log to write down unfamiliar phrases and track how often they are used to better understand different expressions.