There are two different types of images. Raster images (sometimes called “bitmap”) and vector-based images
RASTER AND VECTOR
OVERVIEW OF IMAGE TYPES
A raster image is made of thousands of little dots, or pixels. Creating or editing an image with dots allows you to provide for rich detail in an image. Because every dot can be a different color, you can allow for any kind of color change. Raster images are file-heavy. All of the zeros and ones that are used to make up each pixel result in large files sizes. Rasters do not resize well. When you resize a raster image, the pixels just get larger, making the image appear distorted and chunky/grainy. Photo editors, like Adobe PhotoShop, use raster-based images.
Vector-based programs approach image creation in an entirely different manner. A vector-based program does not render images on a pixel-by-pixel basis. In a raster-based image creation program, a square would be made of thousands of pixel dots. In a vector-based program, the same square would be made of only four dots, one on each corner. These “vector points,” basically allow your computer to play Connect the Dots. Each vector point has information in it telling your computer how to connect each point with straight or curved lines, and with what color to fill in the closed shape. Because the computer only has to keep four points in its memory, it is much easier for the computer to edit vector-based images. If you resize a vector-based image, it loses no detail. The vector points spread out and the computer just redraws the image. You can easily color, or recolor, a vector-based image very easily. Vector images do have some drawbacks, however. They are generally filled with a solid color or a gradient but can’t display the lush detail of a raster based image such as a photo. Illustration programs like Adobe Illustrator and CorelDraw use vector-based images.