Screen Printing involves creating a stencil, known as a screen, and then using that screen to apply ink on the printing surface. Each individual color is applied using a different screen, one at a time, combined to achieve the final look. The more colors a design has, the more screens that are needed, and the more setup time required.
The ink in screen printing is applied thicker than digital printing, which results in brighter colors - even on darker shirts. Screen printing is the best option for designs that require a high level of vibrancy, specialty products, or for quantities greater than 50 pieces.
Digital Printing is a much newer process that involves your artwork being processed by a computer, and then printed directly onto the surface of your product. Digital printing is not a transfer - the ink is directly adhered to the fabric of your shirt. The fact that the design is processed and printed digitally allows for a quantity of one, since there are no screens or physical setup.
Digital Printing is best used for items that require large amounts of detail and/or print colors, customers that require water based ink, and for orders of a smaller quantity. The fact that the digital printer does not use screens allows for a print with much more detail than traditional screen printing. As the ink is applied thinner, digital printing is best used on lighter colored shirts to allow the design to shine through.