Passport stamp

A passport stamp is a rubber stamp inked impression received in one's passport upon entering or exiting a country. Passport stamps may occasionally take the form of sticker stamps, such as entry stamps from Japan. Depending on nationality, a visitor may not receive a stamp (unless specifically requested), such as an EU/EFTA citizen travelling to an EU or EFTA country. Most countries issue exit stamps in addition to entry stamps. A few countries issue only entry stamps, including Australia, Canada, United States, New Zealand, Ireland, and the United Kingdom. Hong Kong, Macau, Cuba and Israel, (among others), do not stamp passports upon entry nor exit, but issue landing slips instead. Visas may also take the form of passport stamps.

Immigration authorities usually place stamps in passports at a port of entry or border crossing, as part of their immigration control or customs procedures. This endorsement can serve many different purposes. In the United Kingdom the immigration stamp in the passport includes the formal "leave to enter" granted on entry to the country to a person who is subject to immigration control. Alternatively, the stamps activates and/or acknowledges the continuing leave conferred in the individual's entry clearance. Other authorities, such as those in Schengen Member States, simply stamp a passport with a date stamp that does not indicate any duration and this stamp is taken to mean either that the person is deemed to have permission to remain for three months or an alternative period as shown on their visa. In Japan, the passport entry sticker also contains a QR code that allows the immigration official to electronically collect information related to that entry.

...
Wikipedia