CodeIgniter is a popular open-source web application framework built for PHP developers. It helps developers create full-featured web applications quickly and easily. With its built-in libraries, it simplifies the development process, allowing developers to focus on the creative side of their applications. CodeIgniter also comes with a range of tools for debugging, validation, and data manipulation. It is lightweight and has a small footprint, making it ideal for shared hosting environments. With its wide range of features, CodeIgniter can be used to power a variety of web applications, from small sites to large enterprise applications. With its user-friendly interface and straightforward syntax, CodeIgniter is perfect for developers of all skill levels, from beginner to experienced.