What does whitelisting mean?

In information technology, a "whitelist" - as opposed to a blacklist - is a tool that is used to group together similar elements (such as people, companies or programs) that are trustworthy in the opinion of the list's authors.Adblockers such as Adblock Plus, for example, offer users the option of placing certain websites on a "whitelist". Online advertising is no longer blocked on these websites. However, the fact that Adblock Plus itself also maintains a "whitelist" of websites that are generally not blocked by the user is a source of criticism. In order to be added to this whitelist, certain guidelines must be adhered to, and payment is often required.