A tab is a kind of card index, displayed on a screen. As with card indexes, a user can choose an individual card - called a tab page - by choosing its title. Tabstrip controls are an easy way of displaying and navigating between the various components of an application on a single screen. Unlike conventional screen sequences, the user can see all of the pages to which he or she might need to navigate on a single page.
For further information about using tabstrip controls, see the online documentation. Choose "Basis -> ABAP Workbench", followed by either "SAP Style Guide" or "ABAP Workbench Tools".