Which of the following describes a 'macro' in FANUC programming?

In FANUC programming, a 'macro' refers specifically to a predefined set of motions or operations that can be reused throughout a program. Macros allow programmers to simplify complex processes by encapsulating a sequence of commands, which can be executed repeatedly without rewriting the code. This not only improves programming efficiency but also enhances readability and reduces the risk of errors since the same code can be called multiple times with different parameters as needed.

While the other options describe essential programming concepts in their own right, they do not accurately convey the primary function of a macro. A conditional statement pertains to decision-making logic within the code, variable storage methods relate to managing data types and using variables, and serial communication protocols involve how devices communicate data, which is unrelated to the definition of a macro. Thus, understanding macros as a tool for streamlining programming practices in FANUC helps reinforce their critical role in automation and CNC programming.