What are Custom Tabs in salesforce and their types ?

Custom tabs are to display data of the custom object or any other web content built into the salesforce application.

1. Custom Object Tabs - it displays the data of your custom objects in a user interface tab. Custom object tabs look and function just like standard tabs.

2. Web Tabs - custom web tabs are used to display any external application or web page.you can include the sidebar or span across the entire page without the sidebar. It is mainly used for any third party integrated application or any web page.

3. Visualforce Tabs - They display data from a Visualforce page. Visualforce tabs look and function just like standard tabs.

4. Lightning Page Tabs- To make lightning components available in lightning experience ,we have to make a lightning component tab.