Raster may refer to any of the following:
1. A raster image is an image file format that is defined by a pixel that has one or more numbers associated with it. The number defines the location, size, or color of the pixels. Raster images are commonly .BMP, .GIF, .JPEG, .PNG, and .TIFF files. Today, almost all of the images you see on the Internet and images taken by a digital camera are raster images.
One of the biggest disadvantages of a raster image is the inability to resize the image without getting jaggies or another type of distortion. For example, if you have a small raster image that you increase the size of it will become distorted because the image editor is resizing each of the pixels in the image.
Because of this disadvantage many printing companies that print business cards, posters, or any other large printing will require that the image be a vector image. Vector images are used for logos, graphics, and text because of the ability to be resized in any direction without distortion.