Not all statements correspond to actions. For example, you might want to inform the computer of some important fact. Flow control . Flow control decides when and where statements are executed. It is the master plan that hangs all the statements together.
Some commands exist just to provide flow control.
In traditional programming, we imagine our program as a little man running from one station to another inside a factory. Using flow control commands, we can organize the man's schedule so that he keeps the factory running. In OOP, we have a factory full of people who stay inside cubicles. Parts are passed inside the various cubicles, where they are processed, and then passed out again. To keep this factory running, you have to understand the function of each cubicle.