A shih tzu is a toy dog breed weighing 5–7.25 kilograms (11.0–16.0 lb) with long silky hair. The exact origins of the breed are unknown, but it is thought to have originated in Tibet and then been developed in China although various hypotheses exist. The name comes from the Chinese word for "lion dog" and is both singular and plural.
Source: http://en.wikipedia.org/wiki/Shih_Tzu