Answer:
First of all, the term "waiver" comes up in Immigration law more than once and, in more than one case the term is related to a visa. Most commonly, "visa waiver" and "waiver of inadmissibility."
There is a difference between a visa waiver and a waiver of inadmissibility. A visa waiver applies when a qualifying alien comes to the United States without formally applying for a waiver at a US consulate.