guides/developer/Developer-guide.md

-Version 0.4
+Version 0.4.1
 -----------
 
 Welcome to the Developer’s guide.
@@ -39,12 +39,26 @@ The easiest way to start developing your own component is to pick an
 existing one which is closer to your needs and modify it to fit your
 requirements.
 
+### Path extractors
+
+Path extractors are used by the spider and their only job is to extract and return
+a list of paths from the provided HTML document.
+
 ### Modules
 
 Modules are the most important type of component in the framework.<br/>
 They assess and log vulnerabilities or other entities of interest during
 the scanning process.
 
+They operate under the scope of a page and are passed each page that needs to be
+audited.
+
+They are split into 2 categories, _audit_ (active)  and _recon_ (passive).
+Audit modules actively engage the webapp via its inputs while recon modules
+perform discovery related operations like checking for certain patterns in
+the page body or look for interesting files and directories on the server.
+
+
 ### Reports
 
 Reports are used to export the results of the audit in a desired format or fashion.
@@ -62,8 +76,16 @@ it what it pleases.
 
 Via the framework they have access to all Arachni subsystems and can
 alter or extend Arachni’s behavior on the fly.
-Plug-ins run in parallel to the framework and are executed right before
-the scan process starts.
+Plug-ins run in parallel to the framework (and each other) and are executed right before
+the scan starts.
+
+### [RPCD Handlers](http://support.arachni-scanner.com/kb/rpc-api/writting-dispatcher-rpcd-handlers)
+
+RPCD Handlers are server-side components which have direct access to their parent
+Dispatcher and whose API can be exposed via the regular RPC interface.
+
+These components provide a way to extend the server-side functionality with
+extra features.
 
 [Core API](http://rubydoc.info/github/Arachni/arachni)
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