A more thorough explanation:

An ambassador is a high-ranking diplomatic officer who is appointed by a government to represent their country in a foreign state. They are the official representative of their country and their role is to maintain good relations with the host country and protect the interests of their own country. Ambassadors are usually appointed by the head of state or government and are given many privileges while abroad, including immunity.

For example, the United States has an ambassador to China who is responsible for representing the interests of the United States in China. The ambassador is the highest-ranking American diplomat in China and is responsible for maintaining good relations between the two countries.

Ambassadors are different from ministers and envoys, who only represent the state they are from and not the sovereign. They are also different from certain legates who have only ecclesiastical authority. However, some legates, such as the papal nuncio and the legate a latere, bear the rank of ambassador.

There are different types of ambassadors, including:

• Resident Ambassador: An ambassador who resides in a foreign country as the permanent representative of a sovereign or nation.
• Ambassador Plenipotentiary: An ambassador who has unlimited discretionary powers to act as a sovereign's or government's deputy, especially to carry out a particular task, such as treaty negotiations.
• Ambassador Extraordinary: An ambassador who is employed for a particular purpose or occasion and has limited discretionary powers.

Overall, ambassadors play a crucial role in international relations and are responsible for representing their country's interests abroad.