A digraph is a combination of two letters that together represent a single sound or phoneme in a language. Common examples include "ch" in chair, "sh" in shoe, and "th" in this. Digraphs can be found in many languages and are essential for understanding pronunciation and spelling. In English, digraphs can be categorized into two types: consonant digraphs and vowel digraphs. Consonant digraphs, like "ph" in phone, create a unique sound, while vowel digraphs, such as "ai" in rain, represent a specific vowel sound. Recognizing digraphs helps improve reading and writing skills.