What is a function in programming?

A function in programming is indeed described as a reusable block of code that performs a specific task. This concept is foundational in programming as it promotes code modularity and reusability, allowing programmers to write code once and utilize it multiple times throughout their application. Functions can take input in the form of parameters, process that input, and often return an output. This capability not only streamlines the code but also makes it easier to maintain and understand.

In contrast, other options do not adequately describe a function. A group of variables does not encapsulate behavior; it simply represents data without any associated operations. While error handling is important, it is not the primary definition of a function. Furthermore, an array of data is a structured collection that can hold multiple values but does not execute any operations or tasks. Therefore, the best description of what a function is in programming is that it serves as a reusable code block designed for specific tasks.