App Store search results are based on several factors determined by Apple-confidential algorithms.
The fields that are weighted most heavily for the search are the names, keywords, and company names of apps, and these are requested during the building process of your application.
Of course, there can be several pages of search results, and your app may not appear on the first page depending on the frequency/popularity of the words/phrases used.
Finally it is good practice to ensure you provide the most relevant and detailed screenshots of your application to make sure end users looking specifically for you can identify your app at a glance.