Anyone who has studied the field of science and engineering should have heard the word "control" once. In particular, "automatic control" is often used in the field of science and engineering. The field of control is so deep that one specialized book can be written by itself, but this time, let's take a brief look at "What is control?". We will discuss the difference between automatic control and manual control, the difference between feedback control and feed-forward control, and the relationship between artificial intelligence and edge computing, which have become popular in recent years. What is the definition of control?