what config<application-config>,<components> in portalapp.xml file

Hi all,

I have gone through the documentation of portalapp.xml..

there i have found various parent tags in portalapp.xml

i am confused about the following tags can any one tell me what to configure under these sections

1)<application-config></application-config>

2)<components></components>

3)<component-config></component-config>

4)<component-profile></component-profile>

Thanks and Regards

Prasad.Y