The screen window of a screen refers to the number of holes or openings per linear inch or centimeter in the screen material. In other words, it's the measure of how many wires or threads are woven together per inch or centimeter of the screen.

For example, a screen with a mesh count of 100 would have 100 openings per linear inch, while a screen with a mesh count of 200 would have 200 openings per linear inch. The higher the mesh count, the smaller the openings in the screen material.

The mesh count is an important factor to consider when selecting a screen for a particular application. A higher mesh count screen is generally used for finer filtration or to screen out smaller particles, while a lower mesh count screen is used for larger particles or for applications where higher flow rates are required.

The mesh count can also affect the screen's durability, as higher mesh counts generally result in a thinner screen material that may be more prone to damage. Therefore, it's important to consider the mesh count as well as the material and construction of the screen when selecting a screen for a specific application.