"A table that extends another table is called a child class, and the table it extends is the parent class" - this is about halfway down in this link below: https://docs.servicenow.com/en-US/bundle/tokyo-platform-administration/page/administer/table-administration/concept/table-extension-and-classes.html

Explanation/Reference: https://developer.servicenow.com/dev.do#!/learn/learning-plans/orlando/new_to_servicenow/ app_store_learnv2_buildneedit_orlando_tables

Reference:
An application can have as many application menus as the application design requires. An application menu is a container for application modules, which are links to features or functionalities within an application. Application menus are displayed in the application navigator, which is the left sidebar of the ServiceNow interface. Developers can create and configure application menus using Studio or the Application Menus module. Application menus can have different roles and visibility settings, depending on the intended audience and purpose of the application. Reference: [ServiceNow Docs - Application menus], [ServiceNow Docs - Create an application menu]

Reference:
A module is a navigation item that provides access to a feature or functionality in ServiceNow. Modules must have a link type, which determines how the module behaves when clicked. The following is a list of link types:
Assessment. This is a link type that opens an assessment, which is a survey or questionnaire that measures the effectiveness of a process or service.
List of Records. This is a link type that opens a list of records from a table or a saved filter.
Separator. This is a link type that creates a horizontal line to separate modules in the application menu.
Timeline Page. This is a link type that opens a timeline page, which is a graphical representation of the duration and sequence of events or tasks.
The following are not link types, but other module attributes or field types:
List of Records, Separator, Catalog Type, Roles. These are not link types, but a combination of a link type (List of Records), a module attribute (Separator), a field type (Catalog Type), and a user attribute (Roles).
List of Records, Content Page, Order, URL (from arguments:). These are not link types, but a combination of a link type (List of Records), a module attribute (Content Page), a field name (Order), and a link type argument (URL).
Assessment, List of Records, Content Page, Roles. These are not link types, but a combination of a link type (Assessment), a link type (List of Records), a module attribute (Content Page), and a user attribute (Roles). Reference: Modules, Create a Module

https://developer.servicenow.com/dev.do#!/reference/api/paris/server_legacy/c_GlideSystemAPI#r_GS-nowNoT