A tab is the main way to access the objects and Visualforce pages in the application. Without the tab, you will not be able to see object records. The tabs are positioned at the top of the page. You can create new custom tabs to extend Salesforce.com functionality or to build new application functionality. The tabs of standard objects are already defined by Salesforce.com. Therefore, we cannot edit or add standard object tabs. But we can hide or show the particular standard object tab to any custom application. When we come to adding tabs, we can create custom tabs in the Force.com platform. There are three types of custom tabs in the Force.com platform:
Custom object tabs
Visualforce tabs
The Web tab