not to be confused with the Roman Empire of years before, this was pretty much a non-conquering empire (by comparison). It was basically a group of 300 small territories in central Europe. This included Germany, Austria, parts of France and Italy, as well as Russia's neighbours, which later became known as the Eastern Bloc (See warsaw pact). Although not quite a country in it's own right, the hundreds of lands, known to some as the confederation of the rhineland, would unite during wartime to defend thier common interest. Although headed by a general emporer, he had little, if any to some, control over his barons, dukes and knights who declared themselves kings. It was really a pseudo-fuedal kingdom in which one part disliked the next, and did as they pleased. After more than 950 years in existance, it dissolved in 1806, the leading family continuing to rule Austria. It also lead to the creation of Germany.
The holy roman empire was known as the first reich, with the formation of germany the second. Hitler called his regime the third reich to remind people of better times.