When you try search iphone in EBay's search bar, you will get the result like this http://buy.ebay.com/apple-i-phone, And you will wonder how does it works?
First, there is a mapping rule in query analyze procedure. Some query keywords will be modified, because of user's behavior analyze. It helps user, who entered broad meaning keywords in search bar, to more specific keywords. It's different with spellcheck procedure, which is just recommendation.
iphone, iphones, apple i phone are mapping to the same keywords Apple I phone. Site operation team can use tool to customize mapping table.
Second, search results are grouped by commended categories. Search results is differenct due to recommending priority, even with the same mapped keyword. In other words, differenct concealed parameters, but the same url is displayed. FOR EXPLANATION of Best Maching categories for your search & Best Matching Items.
Third, related keywords is group by keywords maching rule. we can find Related Searches & Alternative Searches for mapped keywords, Related Searches is for keyword expend match, in SQL script - like '%keywords%', Alternative Searches is for other related search keywords in EBay's search log.
Fourth, full text search will be performed if no specific search keywords is mapped.