Most search engines show related searches, that may be useful to refine your query. Maybe you don't know too much about "marketing", and you want to find out some marketing strategies. If you type "marketing" at Windows Live Search, you'll see a list of related searches: "internet marketing", "direct marketing", "search engine marketing" etc. In this case, Windows Live Search finds popular queries that contain your keyword.
Google doesn't show related searches in the SERP, except for a small number of queries. They only show one refinement and the first three results. Unfortunately the results are far from perfection, as you can see below:
If you want to see related searches in Google, you'll have to use a trick. Type define: in front of your query, and you'll see a list of related searches. As the define operator is used to find definitions, you'll have to remove it to see the search results.
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