Pressing cloth

A pressing cloth is a bit of fabric that goes under the iron when pressing to prevent heat damage to the garment or other item being pressed.
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You can buy pressing cloths or use scraps of fabric to make your own. I prefer natural fibers, cotton, linen, or lightweight wool. I find that polyester or very thin fabrics are no better than no pressing cloth at all. The purpose of the cloth is to absorb direct steam and heat and distribute it more gently over the surface you are pressing. It helps minimize shine and impressions left by the iron on susceptible fabrics.

Silks are especially susceptible to damage by high heat or steam.   Using a pressing cloth preserves the beautiful shine of the silks I like to use in my applique motifs.  
There is an art to pressing items well and using a pressing cloth helps to give good results.