We are using PRPC 7.1.6.

Couple of questions on publicAPI interface.

1. I can see 21 packages available for different purposes in engine API. com.pega.pegarules.pub is referring public API. Once we click on particular package we can see interfaces,classes, errors, exceptions, enums which are stored in there. Are these all terminology refers same java concept? If so where we can override the methods that is defined in interfaces?

2. pega help says "The keyword tools identifies the PublicAPI interface in Java calls." then how we can refer the below packages where it is not in public API. 
 

Why pega help used general term "class" to represent the public API packages. Because it is having interfaces as well.

The PublicAPI includes these classes: 

com.pega.pegarules.pub.*; // Classes common to most public interfaces. 
com.pega.pegarules.pub.clipboard.*; //Clipboard, Page, and Property 
com.pega.pegarules.pub.context.*; // Requestor, Thread, and Node 
com.pega.pegarules.pub.database.*; // Relational database access 
com.pega.pegarules.pub.dictionary.*; // Dictionary validation interface 
com.pega.pegarules.pub.generator.*; // Java generation 
com.pega.pegarules.pub.pal.*; // Reports statistics about a Thread 
com.pega.pegarules.pub.runtime.*; //Activities, Data Transforms, Whens, Streams 
com.pega.pegarules.pub.util.*; // Miscellaneous utilities