Attribute Set is a collection of attributes, customized to fit a certain type of product. For example, if you sell several different kinds of T-shirts on your website, you can create the T-shirts attribute set which will include the simple attributes commonly shared by all of your T-shirts. This may include color, size, gender, and brand.
Attribute Sets are managed at Catalog > Attributes > Manage Attribute Sets screen in Magento backend:
Managing Atttribute Sets in Magento
