An extension point is an activity or other rule that is designed and intended to be overridden to meet application needs. Many such rules are empty stubs that contain no steps. Typically, the overriding rule is in a derived class.
The Pega Platform itself includes a few dozen extension points. For example, the empty activity Code-Security.ApplicationProfileSetup is executed when an operator logs on. If your application requires special initialization processing for authenticated operators, you can override this application (in your application's ruleset) to perform such processing.
Extension points in frameworks
An extension point is a rule (typically a blank or empty rule) that is marked as an Extension in the Status field on the New or Save As dialog box. The corresponding property Rule-.pyMethodStatus does not appear on the rule form, does not affect rule resolution or execution of the rule, and cannot be changed.
For example, a flow in a framework may include an Integrator shape that connects to a customer master file database. In the framework ruleset, this can be an empty activity with an activity type of Connect, marked as an extension. When rulesets are an implementation of that framework, the developers must override the empty activity with a functioning interface to their customer master file.