Which of the following describes a while loop?

A while loop is a programming construct that repeatedly executes a block of code as long as a specified condition evaluates to true. This type of loop is particularly useful when the number of iterations is not known beforehand and is dependent on dynamic conditions during runtime. It continues to run until the condition no longer holds true, making it flexible and powerful for various programming scenarios.

The other options do not accurately describe the nature of a while loop. A fixed number of iterations is characteristic of a for loop, rather than a while loop, which is condition-driven. While loops are not limited to operating solely on lists; they can manipulate various data types and structures. Lastly, while it is possible to use multiple conditions within a while loop, it is not a defining feature; the primary focus is on the singular condition that controls the loop's execution.