What is a passport primarily used for?

A passport is primarily used to identify a person's identity and their country of origin. It serves as an official government document that confirms the identity of the holder, including their nationality and personal details such as name, photo, date of birth, and other identifying characteristics. This authorization is crucial when traveling internationally, as it verifies the bearer’s citizenship, allowing them entry into foreign countries.

The other options do not accurately reflect the primary function of a passport. While travel allowances, international business transactions, and discounts for travel services are relevant in different contexts, they fall outside the core purpose of a passport, which is fundamentally about personal identification and the right to cross international borders.