Final answer:
A function definition describes what a function does, but it does not cause the function to execute; that occurs when the function is called within a program.
Step-by-step explanation:
The statement that a function definition specifies what a function does and causes the function to execute is false. In computer programming, a function definition explains what the function is supposed to do, what inputs it takes (if any), and what it returns (if anything). However, the function does not execute until it is specifically called within the program. For instance, in economics, mathematical functions are used to model relationships, such as the effect of various factors on a student's GPA. A function might be defined as GPA = 0.25 x combined_SAT + 0.25 × class_attendance + 0.50 × hours_spent_studying to represent how a student's GPA can be calculated, but this function does not execute on its own.