How do the positions of governor general and prime minister in the canadian government differ

The Governor General is the representative of the Sovereign in Canada.
The Governor General serves as the Head of State. He is responsible for the appointment of the Prime Minister. He gives the Royal Assent to the bills passed by the legislative in behalf of the Sovereign.

The Prime Minister serves as the Head of the Government. The Governor General, prime minister, and the cabinet form the Executive Branch of Government in Canada. The Prime Minister appoints Ministers of State to assist individual Cabinet Ministers in their executive duties.