Russian sage (Perovskia atriplicifolia) is a classic example of a plant with a confusing common name. The "real" sages are members of the genus Salvia, which includes the common culinary herb Salvia officinalis. Russian sage and the salvias do share the same family (Lamiaceae), but they are quite different plants. The so-called Russian sage is native from Afghanistan to Tibet, while culinary sage originated in the Mediterranean region. Russian sage is a large, shrubby perennial with light blue flowered spires that float above the deeply toothed silvery foliage.
Culinary sage has smooth-edged, tapered leaves, and tends to not grow over 2 feet tall. It is also a celebrated kitchen herb, with strongly scented leaves that were originally used to flavor (or perhaps mask the flavor of) meats. The inedible gray-white stems and leaves of Russian sage don't have a use in the kitchen, but they add four-season interest to ornamental borders.
The foliage of both plants releases a similar, pungent scent when crushed, but I find the scent of Russian sage more reminiscent of another confusingly named but similarly scented plant: sagebrush (Artemisia).