What is a visa?
A visa is a sticker affixed in your passport by an embassy or consulate or at the border. It authorises the bearer to stay in or travel through one or more countries during a limited and specified period. Under the Schengen Agreement, visas issued by the Schengen countries are generally valid throughout the Schengen area.
The country issuing the visa typically attaches various conditions to the visa, such as the time that the visa is valid, the period that the person may stay in the country, whether the visa is valid for more than one visit, etc