What is line-height:1?

Question

It is a question about the appointment of line-height.

I began study of css. line-height: Examples appointing 20px or a unit are often found. It is sometimes line-

Answer 1

According to w3schools and w3.org line-height:1; is valid and means the following: Sets a number that will be multiplied with the current font-size to set the distance between the lines.