The stitch is worked by carrying the thread across the space to be filled and returning underneath the material next to the stitch just made. The process is repeated until the area is filled in. The stitches may be worked in any direction and they may vary in size, for example, when filling in a leaf shape. The skill in making a satin stitch is to make the stitches lie evenly and closely together and to preserve a neat edge to the shape being filled. The longer the stitch, the more untidy and vulnerable it will become.
The satin stitch is also known as the damask stitch.
Source: THOMAS, Mary (1934). Mary Thomas's Dictionary of Embroidery Stitches, London: Hodder and Stoughton, p. 179.