Digital printing on fabric is very similar to the way an inkjet photo printer prints on paper. There are cyan, magenta, yellow, and black (CMYK) ink jets that spray the design onto a substrate. These inks are translucent and the amount of each color that is sprayed on the material determines the end color produced.
When printing digitally, re-creating the color you see on a computer monitor is a pretty easy process, mostly because the computer does all the calculations to determine the amount of cyan, magenta, yellow, or black needed to reproduce that color. By comparison, with screen printing a highly skilled color separator selects the amount of inks that will be transferred to the garment, and how they will be layered. It is a much more labor-intensive process.