The issue navigator is the primary interface through which you will be performing all of your searches in Jira. You can access it by clicking on the Issues menu in the top menu bar and then selecting Search for issues.

The issue navigator is divided into several sections. The first section is where you will specify all of your search criteria, such as the project you want to search in and the issue type you are interested in. The second section displays the results of your search. The third section includes the operations that you can perform on the search results, such as exporting them into various formats. The fourth and last section lists a number pre-configured, and user-created filters.

When you access the issue navigator for the first time, you will be in the basic search mode. The following screenshot shows the issue navigator in this mode: 

In basic search, as you can see, you specify your search criteria with UI controls, selecting the values for each field. 

If you previously visited the issue navigator and chose to use a different search option, such as advanced search, then Jira will remember this and open up advanced search instead.