Resolution - Binoculars
The resolution of an optical system can be defined as the smallest distance apart at which two points on a target can still be seen as separate entities. Simply put, it is a measurement that shows how well an optical system, in this case, binoculars, can render the fine details of an image.
Of course, this has to do with the magnification factor. However, binoculars of poor quality that have a high magnification factor will still not be able to render the details that top-grade quality binoculars can.
Another term that is often used instead of resolution is resolving power.
Special test charts are used to measure the resolving power. The picture below shows what a test chart can look like and it also shows that you should not do this from your computer screen!