In the biblical Book of Exodus, Aaron was Moses's older brother and spokesman.
Exodus says Moses hesitated when called to confront Pharaoh because he felt he was not an effective speaker. God appointed Aaron to speak for him, describing Aaron as someone who could communicate Moses's messages to the Israelites and to Pharaoh. Aaron therefore served as Moses's public representative during the demand to release the Israelites from Egypt.
Aaron is also presented as the first high priest of the Israelites. Exodus describes his special priestly garments, including the breastpiece, ephod, robe, and turban. His sons became priests as well, establishing a hereditary priestly line in the biblical narrative.
A common mix-up is Joshua, who later succeeded Moses as leader. Aaron's major role belongs to the Exodus and wilderness generation, although the story also portrays his serious failures, including his involvement in making the golden calf. Miriam was Moses's sister, not his brother or spokesman.