If this field is populated then when the product is viewed it will return all products that match the entered information in a 'price compare' type box instead of just displaying a single product and merchant (if the current theme supports it).
To activate it for this product, enter the keywords (separated by spaces) of similar products.
For example '+xbox +halo' (without the quotes) will match all products that contain the words 'xbox' and 'halo' in their names. Prefixing a word with a plus indicates that the word must appear, prefixing with a minus will now match products that contain that prefixed word.
Alternatively, for advanced use, enter a SQL statement. You can get such SQL by copying'n'pasting the generated SQL returned by doing a product search.
Note : setting a value here overrides the global 'Auto Price Compare' setting that is applied at a Site level.
See also Price Compare Syntax.