In Salesforce we can customize tabs as per our requirements. Follow the below steps to customize tabs.
Step 1 : Click All Tabs + Button on the top right corner of the Tabs
Step 2 : Choose the app from the list to perform customize Tab
Step 3 : Click Customize My Tabs Button
Step 4 : Select the Tabs from Available Tabs you want to Add and Click Add Button to move.
Step 5 : Click Save. Now the selected three tabs will be available in the Sales App.
In the same way we can remove the unwanted tabs from an App by selecting the tabs from Selected Tabs list and click remove to move the tabs to Available Tabs list.