Raster images are based on pixels. Here’s a good explanation as defined by “TechTerms.com”
Most images you see on your computer screen are raster graphics. Images found on the Web and photos you import from your digital camera are raster graphics. They are made up of grid of pixels. The larger the image, the more disk space the image file will take up.
Raster graphics can typically be scaled down with no loss of quality, but enlarging a raster image causes it to look blocky and “pixelated.” As you can see in the illustration above, when a raster image is enlarged too much, the image quality is compromised. For this reason raster images are not used to create logos.
File extension: JPG, GIF, PNG, BMP and TIFF are examples of raster images.
Unlike JPG, GIF, PNG, BMP and TIFF images, vector graphics are not made up of a grid of pixels. Instead, vector graphics are comprised of paths. A path can be a line, a square, a triangle, or a curvy shape. These paths can be used to create simple drawings or even typefaces.
In vector images– you can see the blue path lines that comprise the lines, curves, and shapes. Because vector-based images are not madeup of a specific number of dots, they can be scaled to a larger size and not lose any image quality. When you blow up a vector graphic, the edges of each object within the graphic stay smooth and clean. This makes vector graphics ideal for logos, which can be small enough to appear on a business card, but can also be scaled to fill a billboard.
File extensions: EPS, AI are examples of vector images.
What is the Take Away?
All logos MUST BE CREATED AS A VECTOR FILE. Let me say that again…All logos MUST BE CREATED AS A VECTOR FILE!!!
If you do not have your logo in an AI or EPS file format you will have few options to actually use your logo. No matter where your logo is placed or what type of file format your vendor requires. All the various file formats must be generated from the original VECTOR file. So, make sure that your graphic designer has your logo in a vector file. From the vector file any other of the other file types can be generated.
So, make sure your graphic designer is a professional, trusted resource that will supply you with a logo in the vector format.