Vector images are made up of points, lines, and curves that can be infinitely scaled without any loss in image quality.
Vector programs include Adobe Illustrator, CorelDRAW, and Inkscape.
You must use a vector program when designing a logo, and we suggest that you use vector programs for any other print design contest as well.
Raster images are made up of a set grid of dots called pixels, where each pixel is assigned a color value. Unlike a vector image, raster images are resolution dependent. When you change the size of a raster image, you shrink or stretch the pixels themselves, which can result in a significant loss of clarity and produce very blurry images.
Raster programs include Adobe Photoshop and GIMP.
You can use raster programs when designing a website, app, icon, banner ad, or any other design intended for electronic use.
Note: you can use vector programs for any contest on 99designs. However, you cannot use raster programs for logo contests. For more information on vectors and rasters images, see our blog post, The difference between vector and raster images.