Before we go over specific types of resolution, let's cover the two basic ways the term resolution is used. In some contexts, resolution refers to the pixel count of an image. An image with lots of pixels is often called a "high resolution" image. But in other contexts, resolution refers to the density of pixels in a given linear area such as an inch. This "density" is expressed as PPI (pixels per inch) or DPI (dots per inch) and this density number is embedded invisibly in a bitmap image, as an instruction to output devices, such as a printers. For clarity, we will refer to the first type of resolution as pixel count resolution and the second as embedded resolution.