These days, scanning is almost a pleasantly easy task. Printers are often multipurpose and have a scanning function. Software that the printer comes with will guide you through the setup process, and then, once set up, it's a simple matter of placing the page or image you want to scan on the printer, closing the lid and pressing scan. The scanned image will be sent to a location on your computer hard drive that you may have specified earlier and then it is available for whatever use you want to put it to.
There are a variety of scenarios that would require you to do a scan. For example, your accountant might need your P60 document to complete your self assessment. You would scan your P60 and then email it to your accountant. Or you might have a paper photo of someone that needs touching up. The photo, not the person. You would scan in the photo and then perform your amendments in an image editing program like Photoshop. Perhaps you have some sheet music that you need help with; you could scan in the music and then send the scan to your piano teacher (copyright laws permitting).
Software programs like Photoshop and Illustrator allow users not only to amend existing images (like the photos you scanned in earlier), but also to create images from scratch. When editing existing images (raster or bitmap images), there is a dizzying number of different effects that you can apply, from colour corrections, to blurring and increasing or decreasing contrast. Web designers often have to create images from scratch in the form of vector images. Bitmap (or raster) images are stored as a series of tiny dots called pixels. Each pixel is a very small square that is assigned a colour, and then arranged in a pattern to form the image. When you zoom in on a bitmap image you can see the individual pixels that make up that image. Bitmap graphics can be edited by erasing or changing the color of individual pixels using a program such as Adobe Photoshop. In contrast, vector images are not based on pixel patterns, but instead use mathematical formulae to draw lines and curves that can be combined to create an image from geometric objects such as circles and polygons. Vector images are edited by manipulating the lines and curves that comprise the image.