Keyword Funnel: Keyword funnels track the relationships between keywords used by search engine users. Essentially, these funnels help to categorize keywords as part of a keyword research technique.
Typically, the keyword research process will involve "funneling" keywords to go from broad topics to more specific ideas. For instance, "food" may be too general of a keyword. That may get narrowed down to "Mexican food," which would then become more specific with "modern Mexican cuisine," to specific foods such as "beef tamales" to long-tail keywords like "how to fold a burrito." Keyword funneling helps to identify a particular need for a search to appeal to users who need specific information.
A good example of an application that uses a keyword funnel is Google AdWords. AdWords is able to group keywords based on similar searches and search results within their search engine. For example, someone looking for keywords and keyphrases related to "social media" in AdWords might also find results such as "social networking," "social media for business," "top social networks," "facebook," and other related terms.
Some keyword funnels on search engines also take into account spelling errors, so if search engine users frequently misspell a certain word, like writing "iPhone" as "i phone" or "i-phone," Google will show the results for the corrected word instead. Search engines may also show related results for searches that have poor search relevancy (i.e. not enough results) or they may refine queries based on additional keywords. These types of searches are meant to understand the intent behind a user's query.