Decoration covers the techniques used to mark, texture, or pattern a piece's surface, distinct from glaze itself and from when a decoration is applied relative to the glaze layer (see Decoration timing on the Glaze article for that separate axis). Many of these techniques work on bare clay, before any glaze is involved at all.
Sgraffito scratches through a layer of slip to reveal a contrasting clay color beneath. Mishima presses colored slip or clay into carved or stamped lines, then scrapes the surface level so the inlay shows only where it was pressed in. Slip trailing draws with slip directly, squeezed from a narrow-tipped applicator, building up a raised line rather than removing anything. Carving cuts a pattern or relief directly into the clay body itself. Burnishing polishes bare clay to a smooth sheen with a hard tool rather than adding any material at all. Agateware blends two or more different-colored clay bodies together before forming, so the pattern runs through the material itself rather than sitting on its surface.