Strathmore is synonymous with bristol. Bristol is a dense and relatively smooth paper board that is ideal for detail or design work.
Because it is smooth, works produced on bristol reproduce very sufficiently. Because it is dense, ink and marker can find enough surface to allow for intricate detail.
Bristol is measured in plys. 300 series is what students use, 400 series is more professional. 'Vellum' bristol has some tooth on the surface, 'plate' bristol is perfectly smooth.