CAD Exam Dumps : Certified Application Developer - ServiceNow

 Tables that extend a table inherit the parent’s fields. Extending a table means creating a child table that shares the same columns and business logic as the parent table. For example, the Incident table extends the Task table, which means that all fields defined on the Task table are also available on the Incident table. Extending a table allows for reusing existing fields and behaviors without duplicating them on multiple tables. Reference: Table extension and classes

Enabling “Allow access to this table via web services” allows authenticated users with proper roles to access this table via REST/SOAP APIs.

From Development Handbook 4.0.4, p. 191:

"This setting allows web service access to a table, but still requires that users have appropriate roles and permissions through ACLs."

Thus, access isn’t automatic — proper access controls still apply.