There are many types of decorating. Below are the basic definitions of each style:
Method in which ink is applied directly to the surface to be printed (a tee shirt). The image to be printed is photographically transferred to a very fine fabric (the screen) such that the non-printing areas are blocked off and the fabric serves as a stencil. The ink is wiped across the screen to pass through the unblocked pores and reach the tee shirt. For each color to be printed a separate screen is prepared and the process is repeated.
This is the most common type of decorating. This process is priced based on the number of locations and the number of colors in your design, as well as the number of items that will have the exact same print.
This is the process of sewing the design onto a garment using an embroidery machine. This process is based on the number of locations and number of stitches a design will have and not based on the number of colors. Embroidery is not the best option for designs with intricate detail, or designs that are large. Additionally, embroidery is not typically done on tee shirts, as the weight of the thread and backing may weigh the fabric down slightly.
The numbers you see on the back of youth football jerseys are applied with a heat press. The design is cut out in vinyl material, and then it is applied with a commercial heat press. The material is thicker than with screen printing, and doesn't have the same soft feel as can be achieved with screen printing, but can be a good alternative for a very low quantity job that has a very simple one color design. Additionally, if you are a sports team or want to have an item personalized, this is the best, least expensive way to go.