Screen printing is a printing technique whereby a mesh is used to transfer ink onto a substrate, except in areas made impermeable to the ink by a blocking stencil. A blade or squeegee is moved across the screen to fill the open mesh apertures with ink, and a reverse stroke then causes the screen to touch the substrate momentarily along a line of contact. This causes the ink to wet the substrate and be pulled out of the mesh apertures as the screen springs back after the blade has passed.
Basically, it is the process of using a mesh-based stencil to apply ink onto a substrate, whether it is T-shirts, wood, plastics or other material.
One colour is printed at a time, so several screens can be used to produce a multi-coloured image or design.