A boolean is a data type used in computer science and programming that can hold one of two values: true or false. It is named after the mathematician George Boole, who developed a system of logic that forms the basis for modern digital circuit design and programming languages. Booleans are essential for making decisions in code, allowing programs to execute different actions based on conditions. In programming, boolean values are often used in conditional statements, such as if statements, to control the flow of a program. For example, a boolean expression might check if a user is logged in, returning true if they are and false if they are not. This simple yet powerful concept is fundamental to creating logical operations in software development.