Indentation refers to the practice of adding space at the beginning of a line of text. It is commonly used in writing to indicate the start of a new paragraph, helping to visually separate ideas and improve readability. In programming, indentation is crucial for defining code blocks, making it easier to understand the structure and flow of the code. In many programming languages, such as Python and Java, consistent indentation is necessary for the code to function correctly. A lack of proper indentation can lead to errors or unintended behavior. Overall, indentation enhances clarity in both written text and computer code.