Context clues are hints in the surrounding text that can help determine the meaning of unfamiliar words. There are four main types of context clues: definition/explanation, which directly defines the word; restatement/synonym, which uses a similar word; contrast/antonym, which contrasts the word's meaning; and inference/general context, which relies on common sense to infer the meaning. Understanding context clues can help readers comprehend new vocabulary from context in what they are reading.