String functions are built-in operations in programming languages that allow developers to manipulate and analyze text data. These functions can perform tasks such as finding the length of a string, converting it to uppercase or lowercase, and extracting specific parts of the string. Common string functions include length, substring, and replace. Using string functions can simplify coding by reducing the amount of manual text processing needed. For example, a substring function can easily retrieve a portion of a string, while a replace function can change specific characters or words within the text. These tools are essential for effective data handling in software development.