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

If no unit is supplied e.g. "line-height: 1.5" the distance between the lines is set as this number multiplied with the current font size.

1.5 x font-size