A characteristic of an item in a category. For example, "Optical Zoom", "Brand", and "Megapixels" could be aspects of the Digital Cameras category. Aspects are well-known, standardized characteristics of a category, and they vary from category to category (the aspects of "Men's Shoes" are different from those of "Digital Cameras"). A search request on the eBay site will often display aspects and their respective aspect values on the left-had side of a query response.
Aspects are extracted from item listing properties (such as item titles and subtitles), and represent the characteristics of active items. Values returned in the Aspect container can be used as inputs to the aspectFilter fields in a query to distill the items returned by the query. eBay generates aspects dynamically from the items currently listed; aspects provide a view into what is currently available on eBay. Because of this, aspect values returned one day cannot be guaranteed to be valid the next day.
The following graphic shows how eBay might return a set of aspects for the Digital Cameras category. In this graphic, "Product Type", "Brand", and "Megapixels" are aspects, and "Point & Shoot", "Canon", and "12.0 to 12.9 MP" are aspect values. Histogram values (item counts) are shown for each aspect value.