Heat press is a machine that transfers designs onto materials like t-shirts using precisely controlled heat, pressure, and time. It's a versatile tool used by hobbyists and businesses to apply designs from heat transfer paper or heat transfer vinyl (HTV), and can also be used for mugs, hats, and other items. The process involves placing a pre-printed design face-down on the garment, then using the heat press to apply heat and pressure, causing the ink or vinyl to adhere permanently to the fabric.