Character case refers to the distinction between uppercase and lowercase letters in written language. Uppercase letters, also known as capital letters, are typically used at the beginning of sentences or for proper nouns, while lowercase letters are used for most other text. This differentiation helps convey meaning and structure in written communication. In computing, character case is important for programming and data entry. For example, in many programming languages, the variable names variableName and variablename would be considered different due to their differing cases. Understanding character case is essential for effective communication and accurate coding practices.