Screens are used in the printing process to create the illusion of a solid image. The magnified area of the butterfly demonstrates how the tiny dots blend to bring us an image that gives no hint to the naked eye of the thousands of dots used to build it.
Process vs. Spot Color
When a color needs to be accurately reproduced time after time, a "spot" color can be specified. A spot color is a solid color, instead of a blended or "process" build. The most commonplace spot colors are called Pantone. We do offer some custom colors in spot colors. If we do not have that spot color ribbon in house we will then use the CMYK process to build the color.
Vector vs. Raster
There are two main types of design software used for the printing industry. The first is called "raster" or pixel based imagery. You may be familiar with Adobe Photoshop, which is a raster based image editing software. The other type is called "vector" imagery. Vectors are mathematically defined shapes, which can be reproduced at any size with no change in quality. As you can see by the different levels of zoom, pixel based images lose quality when expanded, or magnified. Whereas the vectors recalculate the curves to maintain the integrity of the shape.