The Origami Forum

I can't find anything about this please tell me what is this ?

A reference point is an intersection between two creases (or a crease and an edge) that you fold through.
Unless your talking about something completely different...

A couple of answers here.

It essentially refers to a point which is used as a reference for other, major, creases.

For example, in this post by Jared, folding the angle bisector (22.5 degrees) on the left side and then folding from the right-bottom corner to where the previous crease meets the top of the page, you get a crease which intersects the diagonal where a few meets a few important creases.

Once that point on the diagonal (the reference point) is found, the rest of the creases can be found.

It's used mostly for crease patterns. Of course, there are times when a set of diagrams has a few creasing and uncreasing steps at the beginning to find a reference point, but it's not usually pointed out.
I believe that Dr. Lang sometimes gives you the option of simply measuring and marking the references yourself by pointing out which steps are to find the references. Maybe other designers do the same.