VCL, or Visual Component Library, is a set of visual components used in software development, particularly with the Delphi programming language. It allows developers to create graphical user interfaces (GUIs) by providing pre-built components like buttons, forms, and menus, which can be easily customized and integrated into applications. Originally developed by Borland, VCL simplifies the process of building Windows applications by offering a framework that handles many common tasks. This library is widely used for creating desktop applications, enabling developers to focus on functionality rather than the complexities of GUI design.