Given the task definition and input, reply with output. Given a travel related situation, and given a specific question about the situation, summarize the question into a title

I see many questions here refer to a US "visa stamp", or "getting a visa stamped" for the US, and I often find it difficult to imagine what is going on with this stamp.


Is it the visa sticker itself that is being referred to as a "stamp"? (This wouldn't be quite as crazy as it sounds -- a postage stamp is a sticker, after all -- but on the other hand such a usage is not evident for any other country's visa stickers).
Or is it the admission stamp in one's passport (showing immigration category and how long a stay one has been granted) that people call a "visa stamp", despite not actually being a visa?
Or do (some classes of?) US visas actually need to have some kind of ink stamp applied to them in order to be valid?



What's the deal with "stamping" US visas?