Toyotomi was one of the major figures in uniting Japan into one country where it had been a patchwork of feudal kingdoms that often fought one another.
Toyotomi was born a commoner in the 1530s. Although he was not of samurai stock, he rose to become an important warrior. He attached himself to Oda Nobunaga as Oda worked to unify Japan under his own leadership, eventually becoming Oda's top general. After Oda was assassinated, Toyotomi (who was not yet called that as he did not actually have a surname at that point in his life) took over leadership.
Toyotomi then consolidated power in his own hands, bringing Japan closer to unification. He is seen as one of three (Oda Nobunaga and Tokugawa Ieyasu are the others) great unifiers of Japan.