The term "tab key" refers to a button on a keyboard that, when pressed, helps you move quickly to the next designated spot in a document or form. Full definition
For moving to next top menu item, press tab key. (menswearhouse.com)
Microsoft also super charged the alt - tab key command with access to all apps in all desktop instances. (thenextweb.com)
In the browser, test you can interact with all online content by navigating around a website, webpage or form using only the keyboard (eg TAB key, Enter key). (moneysmart.gov.au)