The word waiver (verb: to waive) has several different meanings: 1. It is a voluntary surrender or relinquishment of some known privilege or right. 2. It is the instrument (document) by which such a surrender or relinquishment is effected. 3. In insurance, it is a supplementary clause or agreement which is attached to a policy; it excludes specific losses, limits how much can be claimed to a specified amount, or extends cover to include items not listed in a standard policy.
It may be either an action or a document. It essentially removes a potential or real liability for the other party in an agreement.
A waiver may be a signed document that shows that a party intends to relinquish their right or claim. It is a voluntary relinquishment, and may apply to a wide range of legal situations.

Waiver in court
For example, when one party is suing another in court, the plaintiff (person doing the suing), by means of a waiver, relinquishes the right to continue suing the defendant as soon as the settlement is finalized.
Governments or regulatory agencies may issue waivers to exempt commercial enterprises from certain regulations. For example, in the US, the size of banks is regulated, but when financial institutions exceed these sizes, they may be exempted.
What is a Visa Waiver?
A Visa Waiver is a program that some nations have that allow specific foreigners to enter the country for a given period without having to obtain a visa. In the United States, this is known as VWP (Visa Waiver Program).

All countries selected for the US VWP are advanced economies (rich nations) with an extremely high Human Development Index, such as all European Union member states (except for Romania, Poland, Cyprus, Croatia and Bulgaria), Switzerland, Norway and some other European countries, Japan, Australia and New Zealand.
Etymology of the verb ‘waive’
Etymology is the study of the origins of words, and how they evolved over history. People who specialize in etymology are called etymologists.
According to the Online Etymology Dictionary, in the British Isles, the word emerged in the thirteenth century, with the meaning ‘deprive of legal protection’. It came from Anglo-French Weyver meaning ‘to abandon, waive’, which originated from Old French Guever ‘to give back, abandon’.
Etymologists believe the source was Scandinavian. The Old Norse word Veifa meant ‘to swing about’.