Product attributes are used to define the characteristic or feature of a product (e.g. power rating, size, etc.) and are displayed in the Specifications tab of a product detail. 

Product attributes are also displayed in the Product Comparison module control. See Product Comparison for more information.

It is also used in the Product Filter module control for refining results. See  for more info.

You must first enable the Product attributes feature under Configuration > Product. Once enabled, you can define product attributes under the Catalog > Attribute groups and Catalog > Attribute definitions menus.