I was recently asked about the results that appear when you search from a specific view so I thought it would be a good topic to write about. I'm going to discuss Global Search, View Search, and Associated View Search.
Global & View Search
Using the search box in the blue bar at the top of the CRM window, will return results across all entities that are search enabled via System Settings. Using the smaller box when looking at an entity view will return results for just that entity. The results that are returned will depend on the Quick Find view settings. For example, if the Opportunity Quick Find view is filtered to show only open opportunities, then your search will return only the open opportunities that meet your criteria.
Associated View Search
If you're looking at an associated view and use the search box from here, it will only return results within this view. This could be helpful if there are several associated records that you need to search through.