How do I change the name of the tabs or hide them?

As an admin on the account, you can edit the name of the different tabs and hide them if needed. When you make these changes it will change the tabs for the entire account. Any user logged in when you make these changes may need to refresh their page to see the changes. 

Let's say you want to change the name of the tab Contacts to Clients. 

You'll need to go to Settings > Navigation Tabs.  Find the tab you need to change, in our case Contacts, and click the Edit pencil to the right of the name of the tab. Type in the new name in both a plural and singular version of the word, so our example of Clients, you would type Clients and Client. And then click Save.

You can also rearrange the tabs on this screen. The plus sign and arrow combo icon allow you to move the tabs to a different order. Click and drag the tab to where you would like. 

If you move the tab to Secondary, this will make the tab be listed under More. If you move the tab to Hidden, this will hide the tab, and no longer be accessible to you and your users. You can always unhide the tab if needed.