When the output of a typical Q-switched laser is focused onto a solid target, a short-lived, localized plasma, characterized by very high ion and electron densities and by very high temperatures, is formed. The present article begins with an outline of the essential features of the laser systems used to generate such plasmas followed by a summary of some concepts in plasma physics necessary for their proper interpretation. The theory of the evolution of the plasma is presented in terms of a hydrodynamic model and the relationship between laser irradiance and plasma temperature is discussed. Several of the more important methods used for studying plasma properties, including inter-ferometry, mass-spectrometry and optical and X-ray spectroscopy, are described and the results for some typical plasmas are presented.