• Site (Liferay 6.1 on wards. Till 6.0 it was know as Community)
• Organization
• Role - Permission
• User Group

• User can have role. Roles are further scoped by Organization, Sites or Regular (Portal Level)
• Ex. User A can have Administrator role for Site-a but for Site-b he is just normal user.
• Each Role is group of Permissions.
• For each Site, there will be one role called Site Administrator which has full access for that site(Super User). Similar is applicable for Organization.
• Apart from Site and Organization Administrator, there is one more role called Site Owner and Organization Owner which is similar to Site / Organization Administrator. 
• The only different between them is Site / Organization Owner can make other user Administrator for that Site / Organization while simple Administrator can't do it.

• You need to refer Liferay class
• You are writing Liferay hook plugin and you want to override existing JSP.
• You want to debug existing Liferay classes in debug mode to understand the flow.
• You wan to see out of the box properties defined in portal.properties file

Once this is done, you can unzip it at some place (e.g. c:/dev).

Once its unzip, follow below steps to configure Liferay source into eclipse.

STEP 1. Right click at package / project explorer and choose Import.

STEP 2. Click on Existing Projects into Workspace.

STEP 3. Point the directory where you unzip liferay source from Browse button.

STEP 4. Once its imported, it will be available in project / package explorer in eclipse.

and its done. Its good practice to configure Liferay source when you do development so that whenever you need to refer any out of the box code, it will be handy. 

Feel free to ask questions / Suggestions 

I would recommend looking at index page 'A Complete Liferay Guide' to browse all topics about liferay.

admin.email.from.name=Test Test
default.admin.first.name=Test
default.admin.last.name=Test
liferay.home=C:/Liferay Developer Studio 1.5/resources/liferay-portal-6.1.10-ee-ga1
[email protected]
company.default.name=Liferay
[email protected]
company.default.locale=en_US
setup.wizard.enabled=false
default.admin.screen.name=test

• Any properties defined in portal.properties file, can be overridden in portal-ext.properties defined at location-1.
• Any properties defined in portal-ext.properties file at location-1, can be overridden in portal-ext.properties defined at location-2.

@Override
 public void render(RenderRequest request, RenderResponse response)
   throws PortletException, IOException {
  String newProp = PropsUtil.get("test.property");
  String existingProp = PropsUtil.get("company.default.web.id");
  
  request.setAttribute("newProp", newProp);
  request.setAttribute("existingProp", existingProp);
  super.render(request, response);
 }

• We have override render method which will be called when this portlet get rendered on liferay page.
• In this method, we are reading properties defined in portal.porperties (or portal-ext.properties) by util class called PropsUtil.get() method. We are passing Key of property. This method will return value (in form of 'String' if present) or null if property is not defined.
• We are setting properties value in request attribute which will access it in view.jsp

<%@ taglib uri="http://java.sun.com/portlet_2_0" prefix="portlet" %>

<portlet:defineObjects />

Existing Properties is <b>${existingProp}</b><br>
New Properties is <b>${newProp}</b>

• In view.jsp file, we are showing the value of properties by EL.