What is a hidden line and what of this uses and propose of this line?

Answer:
A hidden line, also known as a hidden object line is a medium weight line, made of short dashes about 1/8” long with 1/16”gaps, to show edges, surfaces and corners which cannot be seen. Sometimes they are used to make a drawing easier to understand. Often they are omitted in an isometric view.
Explanation:
HOPE IT HELPS