A code library is a collection of pre-written code that developers can use to perform common tasks without having to write the code from scratch. These libraries often contain functions, classes, and methods that simplify programming and help save time. They can be specific to a programming language, such as Python or JavaScript, and are widely used in software development. Code libraries can be open-source or proprietary, and they are often shared through platforms like GitHub. By using these libraries, developers can focus on building unique features for their applications instead of reinventing the wheel for standard functionalities.