The Ostrogoths were the eastern branch of the later Goths. The other major branch was the Visigoths.
The Ostrogoths started with the Greutungi, a branch of the Goths that moved southward from the Baltic Sea during the 3rd and the 4th centuries.
They built an empire that stretched from the Black Sea to the Baltic Sea and traded with the Roman Empire. Its peak was under King Ermanaric.