A "boucle" or loop is a programming structure that repeats a set of instructions until a specified condition is met. It allows developers to automate repetitive tasks, making code more efficient and easier to manage. Common types of loops include the for loop, while loop, and do-while loop, each serving different purposes based on the situation. In everyday applications, loops are used in various scenarios, such as iterating through items in a list or executing a block of code multiple times. This functionality is essential in programming languages like Python, Java, and C++, enabling developers to create dynamic and responsive applications.