What does 'iteration' refer to in programming?

Iteration in programming refers to the process of repeating a set of instructions or code until a specific condition is met. This allows developers to efficiently handle tasks that require repetitive actions without needing to write the same code multiple times. For example, loops such as "for" or "while" are commonly used structures for implementing iteration, enabling the execution of the same block of code numerous times.

This concept is fundamental in programming because it helps in automating repetitive tasks, allows for the processing of data collections like arrays or lists, and can simplify code by reducing redundancy. The correct understanding of iteration is crucial for creating efficient and effective algorithms where tasks, such as summing numbers or processing items in a collection, need to occur multiple times based on changing conditions.

In contrast, executing code once describes a single run of a function or statement without repetition, while defining functions repeatedly does not encapsulate the essence of iteration, and combining data types does not relate to the process of repetition in execution. Understanding how iteration works forms a key part of effectively programming in various languages.