Word "vizier" means one who bear the burden. Vizier takes over many resposibilities on his own shoulders, that is why he was called a minister.
The vizier in ancient Egypt was the most powerful position after that of king. Known as the djat, tjat, or tjati in ancient Egyptian, a vizier was the equivalent of the modern-day prime minister of the nation who actually saw to the day-to-day operation of the government in all its aspects. The vizier was not simply a counselor or advisor to the king but was the administrative head of the government who implemented the king’s policies and arranged for the various governmental departments to carry these out.
The vizier was responsible for the operation of the following governmental agencies:
Agricultural – Procedures, practices, settling land disputes
Financial – Taxation, the treasury, and the census
Judicial – The appointment of the judges and the chief of police
Military – The appointment of generals and approval of their choices in subordinates
Architectural – The planning and building of the king’s monuments and tomb
Interior – The planning and construction of roads and repair of dikes, dams, and canals
Religious – The maintenance of proper rituals and traditions and appointment of high priests
In order to perform his duties, the vizier had to be highly educated and knowledgeable in how all these different agencies worked. The vizier had to be literate, and so had to have received training as a scribe, but also needed the skills of an accountant, architect, lawyer, judge, historian, farmer, and priest.
Egyptologist and historian Margaret Bunson gives an overview of the responsibilities of the office:
Viziers were originally chosen from among the king’s relatives, usually a son, starting in the Early Dynastic Period (c. 3150-c. 2613 BCE). The most famous vizier of this time is Imhotep (c. 2667-2600 BCE) who served under the king Djoser (c. 2670 BCE). Imhotep was an exception to the standard practice of choosing a vizier from the king’s family as he was a commoner who achieved his success based on his own accomplishments and personal merit.