What best describes nested loops?

Nested loops are best described as a loop that contains another loop. This means that within the body of one loop, you can have an additional loop that iterates over its own set of values. Such a structure is commonly used to handle multi-dimensional data structures, like matrices or grids, where the outer loop iterates over rows and the inner loop iterates over columns.

This allows for executing a series of instructions for each iteration of the outer loop, effectively creating a layered or hierarchical looping structure. For example, in a scenario where you need to access every element in a 2D array, you would employ a nested loop: the outer loop might traverse the rows while the inner loop accesses individual elements within those rows.

The other options describe different programming concepts and do not accurately characterize nested loops. Functions returning other functions, loops with multiple exit points, and sequences of independent iterations do not encapsulate the specific structure and purpose of nested loops.