In graphical user interfaces (GUIs), a checkbox is a widget that allows users to make a binary choice, such as yes/no or true/false. It is typically represented as a small square box that can be either checked (selected) or unchecked (deselected). Checkboxes are commonly used in forms, settings, and applications to enable users to select one or more options from a set. Unlike radio buttons, which allow only one selection from a group, checkboxes permit multiple selections. They are essential elements in user interface design, providing an intuitive way for users to make choices and input data.