Versions and content of SAP Netweaver...

Hi,

Could someone please point me to the versions of SAP Netweaver?

I would like to know the differences between SAP Netweaver, SAP Netweaver Portal, SAP Composition Environment, etc...

If I download SAP composition environment won't I have the SAP Netweaver Portal?

In SDN, under Downloads/SAP Netweaver Main Releases (http://www.sdn.sap.com/irj/scn/nw-downloads), which should I download?

What does SAP Netweaver contain and what does SAP Composition Environment contain?

Please provide me this information with the view that I am a fresher to SAP...

Thanks,

Agasthi...