A loop is a way of telling your program to repeat a block of code multiple times without having to write it out over and over. Instead of writing the same instruction 100 times, you write it once and tell the loop how many times to run it.

There are three common types. A for loop is used when you know exactly how many times you want to repeat something. A while loop keeps repeating as long as a condition is true — useful when you don't know upfront how many times you'll need to loop. A do-while loop is similar to a while loop except it always runs at least once before checking the condition.

Loops are one of the most fundamental tools in programming and you'll use them constantly across every language you work in.