How to make "annotation" which always face the camera? See the pictures.

I've just started learning Unity and I want to make a project class that can show annotation on my models. I want the annotation rotation to always face the camera like the one in the picture.

I think it will be like making GUI that sticks to camera, but i want this to stick to an object, but once clicked it will always face to camera.

How can I achieve something like this in Unity? Please explain it or give me links to article explaining something like this.