What are these Object Keys ?

Guyz,

i'm kinda' stuck with the concept of 'Object Keys in Configuraiton Objects' in http://help.sap.com/saphelp_nw2004s/helpdata/en/34/393071e9b998438ddb8ce97cd617a1/frameset.htm.

Though I found furhter more explanation in book by Jens Stumpe & Joachim Orb' under section 6.3.2 , 'Key Fields', i'm not unable to comprehend the crux of the whole thing.

Could you anyone of you guide/explain me what it means ? Basically I udnerstand that these sections are pointing to the Keys of various config objects ( Key : I think through which we can identify unique object) but i'm sure i'm not getting complete picture and missing subtleties.

any explanation with some example will be highly appreciated .....

Thanks a ton in advance