Big O notation is a way of describing the speed or complexity of a given algorithm.

Simply, Big O notation tells you the number of operations an algorithm will perform. It takes its name from the “Big O” in front of the estimated number of operations.

What the Big O notation does not tell you is how fast the algorithm will be in seconds. There are too many factors that influence how long it takes for an algorithm to run. Instead, you will use the Big O notation to compare different algorithms by the number of operations they do.