When you select the "Framework and Implementation" option, the application wizard will create the application with both the framework and implementation layer. For example:

Framework:

SAE-FW-HRServices-FW-Work

Implementation:

SAE-HRServices-Work

This allows you to build your application and rules in the framework layer. The Implementation layer rules will simply just be a wrapper that calls the rules in the framework layer. This allows you to create many implementations from the same framework of rules to specialise, e.g. SAE-EnggServices-Work, SAE-CorpServices-Work, which inherit rules from the framework layer. 

This allows specialisation of the rules in the framework in each implementation layer.

You may want to read through this article: https://pdn.pega.com/implementation-methodology-dco/understanding-the-class-structure-and-rulesets-generated-by-the-application-accelerator. Although this describes the class structure built by the Application Accelerator for PRPC 6.x, the general concept of framework/implementation layer is still the same.

Hello,

The application wizard will create classes for the application as per below if Implementation is selected,

TestL-TestImpL-Work

TestL-TestImpL-Data

TestL-TestImpL-Int

while the application wizard will create classes for the application as per below if Framework and Implementation is selected,

TestL-FW-TestImpL-Work

TestL-FW-TestImpL-Data

TestL-FW-TestImpL-Int

Any rule in framework layer can be used in various implimentations.

Think of Application structure as your house. 

Pega code is the whole house

Framework is like a living room (hall)

Implementations are like bed rooms.

If you want your TV to be accessible to all people in your house, you'd place that in your living room. But if don't, you have to put one tv in each room.

Same thing applies here. If you want any rule to be accessible by multiple implementations, you put it in framework. If you want to customize something, you can do it in any implementation. For ex, only one of your bedrooms need a tv but not all. In this case, you'll just buy another TV and put it in your room. People in other rooms will still access the TV in living room. If you have 1 framework and 5 implementations, and you need one customization, you just do it in one implementation layer. All other 4 implementations will use the rule(s) in framework layer.