The golden ratio is a unique number that equals to 1.61803398875.
We find the golden ratio when we split a line into two different parts so that when the longer part is divided by the shorter part, it ks equal to when the whole length is divided by the longer part.
The golden rectangle is when you put the total length of the line that makes the golden ratio for the length then put the bigger part of the line that makes the golden ratio as the width which than gives the golden rectangle