A loop is a programming structure that repeats a block of code multiple times until a specified condition is met. Loops are useful for automating repetitive tasks, such as processing items in a list or performing calculations. Common types of loops include the for loop, which iterates a set number of times, and the while loop, which continues until a condition becomes false. In addition to simplifying code, loops can enhance efficiency by reducing redundancy. By using loops, programmers can write cleaner and more manageable code, making it easier to read and maintain. Overall, loops are fundamental tools in many programming languages, including Python, Java, and C++.