If I'm understanding the question correctly, you are reffering to magnification. 3x Zoom means you are bringing the view of whatever you are looking through (i.e. camera, binoculars, scope) 3 times closer. More than likely there is a magnification ring or lever to zoom the image or view closer. The 4x times zoom means the same thing, you are bringing the image or view 4 times closer with some type of ring or lever.
For your second question: It doesnt really apply to premium optics any differently than it applies to lower quality optics although magnification can vary slightly between manufactures.
MO
