A Search Results query is a piece of configuration that handles how the Search Results web part processes the search. The token variable, {searchboxquery}, passes the input from the Search Box web part into the Search Results web part. On the Properties page of the Search Results web part, you can modify the settings that are available, as shown in the following screenshot:

The Change query button under Search Criteria allows you to add additional query parameters, including result sources for processing queries in this search. Inside this dialog box, you can structure advanced queries using the Kutso Query Language (KQL) or quick queries using simple radio buttons and drop-down selectors. You can also add refiners (properties that are used to group, sort, or categorize content) and configure settings to remove duplicates, rewrite URLs, and specify whether or not you want to use the site's query rules.