Basically, this is a screen printed image produced on a paper liner, which you then affix to the shirt using a heat press (high temperature combined with high pressure).
T-shirt printing, otherwise known as screen printing, is a simple and inexpensive method of printing your own custom designs or logos onto a t-shirt.
Six of the most common t-shirt printing methods are direct-to-garment (DTG) printing, screen printing, dye sublimation, heat transfer vinyl (HTV), plastisol heat transfer, and airbrushing. Direct-to-garmenting printing and screen printing are the two most popular methods.