Resolution is the picture quality displayed on a screen (Desktop, Laptop, Mobile, Tablet, Television Screen). Basically, the resolution is measured by the number of horizontal and vertical pixels. Usually, it is mentioned as width x height, with the units in pixels: for instance, “800 × 600” means the width is 800 pixels and the height is 600 pixels.
Images become crisper when resolution increases, because of a higher pixel density. As more pixels per square inch are being displayed, text and images may also become smaller. When you decrease the resolution, the opposite happens; text and images appear bigger but are not as crisp.