Adding New Assets

What is the difference between Product Name and Asset Name. If I have 10 copies of Office 2003 then the product is MS Office 2003 but so is the Asset Name. To top that the Asset Name is a unique field so I would have to make each asset name MS Office 2003-1, 2003-2 etc. If the asset name is unique then whats the value in having a non unique alpha-numeric string called asset tag, which is a unique value by itself. As I drop down through the fields I hit Expiry Date. Again I am unable to determine the actual function of this field (what expires?) seeing as there is a field for Warranty Expiry. I do like the allocation details but I see I will have to create a query to report software used/available. Any thoughts, guidance on how to properly use these fields is welcomed.

Cheers
Mark