The Rorschach test or ink blot test was developed by Hermann Rorschach, a Swiss psychologist who published his findings in his book, Psychodiagnostik, in 1921. He was not the first person to use ink blot interpretation as a diagnostic tool; however he was the first person to write about it extensively. He studied hundreds of patients and also used hundreds of ink blots; but eventually reduced the number he used to ten. Because the method had been used by many others, he had difficulty getting his book published, and died within a year of its release. After Rorschach's death, his test was refined and improved by a number of psychologists, including Samuel Beck and John Exner.
There is more than one method of evaluating the test, with Exner's version more popular in the United States. Administration normally involves showing the ten ink blots to an individual and evaluating his responses--or lack of response--to the images. The use and interpretation of the images is too complex a subject to be discussed here; however the link cited below provides excellent infomration and examples on the use of the system.