Use of the product attributes

Hi

I have the gone through the inventory manual ,but I did not understand the use of Attributes in AX 2012.

Can anyone explain what is the purpose of attributes and how it differ with product categories ?

Regards

Lally

Product categories are for purchase reqs and the web, so an item might be in the “fan” category, whilst its attributes could be a fan speed of 35mph or a blade size of 7 inches.