I use this term to refer to the physical nature of the surface, which can be perfectly flat (no structure) to grainy, with random groves or with patterns. With reptiles and fish nice surface structures can be seen : snake skin or fish scales. In fashion these attributes are very much appreciated.
Well designed synthetic patterns have a similar visual attractive effect as surface structure and probably relates to an affinity of the human perception for repetition.
In oil painting brush touches are often well integrated with a aesthetic value, so can one also work mechanically on the surface of a curing resin to have a similar effect. The alternative is to use moulds to print these patterns. Also injection moulding or calendering of plastics make use of structured moulds to bring this attribute onto the an object or sheet.
Surface structure on Apix coloured linseed oil based elastomer, obtained with gypsum mould