To further clarify. Imagine, for the sake of a nice example, that MS owned the patent to pinch-to-zoom. Google incorporate pinch-to-zoom in android but don't a

To further clarify. Imagine, for the sake of a nice example, that MS owned the patent to pinch-to-zoom. Google incorporate pinch-to-zoom in android but don't actually sell any product featuring pinch-to-zoom so aren't actually infringing on the patent. Some other company produces an android device and thus creates a product that uses pinch-to-zoom and thus infringes on MS' patent.