A grapheme is the smallest unit of a writing system that represents a sound or a meaning. It can be a single letter, like A or B, or a combination of letters, such as ch or sh. Graphemes are essential in forming words and conveying language in written form. In different languages, graphemes can vary significantly. For example, the English language uses the Latin alphabet, while Chinese uses characters that represent whole words or concepts. Understanding graphemes is crucial for reading and writing, as they help decode the sounds and meanings of words.