A more thorough explanation:

A diplomatic bag, also known as a diplomatic pouch, is a bag that contains official correspondence, documents, or articles that are intended exclusively for official communications of a nation with its missions, consular posts, or delegations. The contents of the bag are considered to be protected by diplomatic immunity and are not subject to search or seizure.

For example, if the United States embassy in France needs to send important documents to the State Department in Washington, D.C., they would use a diplomatic bag to transport the documents. The bag would be sealed and marked with the official seal of the embassy, and it would be transported by a diplomatic courier who has diplomatic immunity.

Another example would be if the ambassador of France in the United States needs to send a confidential letter to the president of France. The letter would be placed in a diplomatic bag and transported to France by a diplomatic courier.

These examples illustrate how a diplomatic bag is used to transport sensitive and confidential information between countries without the risk of interception or seizure.