Final answer:
A variable that holds a value as an indicator of whether some condition has been met is known as a 'flag' or 'boolean variable', usually holding a true or false value.
Step-by-step explanation:
A variable that holds a value as an indicator of whether some condition has been met is known as a flag or sometimes referred to as a boolean variable. Variables are used in programming to store data that can be manipulated and retrieved throughout the execution of a program. In the case of a flag, the variable typically holds a boolean value of true or false representing the state or outcome of a condition. For example, after checking if a user's input is valid, a flag variable might be set to true to indicate validation has passed, or false if it failed.