Computer graphics fall into two main categories vector graphics and bitmap images.
Vector graphics are made of lines and curves defined by mathematical objects called vectors. You can freely resize or magnify vector graphics without losing sharpness, because they are resolution-independent, the number of pixels used to display a vector graphic is determined by the resolution of the monitor or printer, not by the graphic itself. This is because a vector graphic is not converted to pixels until it is displayed or printed. The objects you create using the drawing tools in the In-Design Toolbox are examples of vector graphics.
Bitmap images, also called raster images, are composed of small squares, known as pixels that lie on grids (also known as bitmaps or raster). Bitmap images are the most common electronic medium for such continuous-tone images as photographs or images created in painting programs like Adobe Photoshop. Bitmap images are resolution dependent that is, they represent a fixed number of pixels. As a result, they can lose detail and appear jagged if they are scaled on-screen or if they are printed at a higher resolution than they were created for.