A little research reveals that the concept of an "Aryan Race" is highly questionable.
The origin of the concept was a linguistic (language-based) grouping. It became a physical concept used to describe a "sub-race" of northern Europeans. These "longer-headed" or "Nordic" Caucasians were considered superior by some theorists.
(By strange co-incidence, many of these theorists considered themselves Aryans!)
Many believed that some ancient Germans were descendents of these ancient northern "Indo-Europeans". The concept was used to distinguish between Western Europeans and Semites (Middle Eastern in origin). Hitler conveniently adopted the term and applied it to the physical characteristics of the majority of the German population and set about to "weed out" Semitic People. Naziism was strongly "Anti-Semitic", which basically meant Hitler wanted to stop the growth of Jewish population which threatened what he saw as the "Master Race".