What is the use of search_query table in magento 2?

In Magento 2 search_query database table store the search query, which users have searched using the search box in Magento 2.
— query_text field in a search_query table in stores the value of search string. When User search through site, all of the search entry will be added to search_query table in query_text field.
num_results field used for Number of results for specific word in the site. That field show count of any string search in site.
— popularity field is displayed popularity of specific word in your site, the Biggest number will have the most popular search word for your site.
store_id will show search from a specific store.
There are some other field also available in search_query table but above field is the main field of a table.

You can check from the admin panel, all of the search query will be shown from Search Terms sectino.
Click on Marketing -> SEO & Search -> Search Terms
You will get all the search result grid for your site.

Error during compilation, Incompatible argument type: Required type: \Magento\Framework\DB\Adapter\AdapterInterface.

We can be resolved Compile time error by below way, The error looks like when running compilation command,

Incompatible argument type: Required type: \Magento\Framework\DB\Adapter\AdapterInterface. Actual type: string; File:
app/code/Rbj/CustomForm/Model/ResourceModel/Customform/Grid/Collection.php
[Magento\Framework\Validator\Exception]
Error during compilation

Solutions:

From Magento 2.2.* version we need to pass full class name in__construct()  instead of $connection = null as di argument in Collection.php file.

Replace, $connection = null argument with \Magento\Framework\DB\Adapter\AdapterInterface $connection = null  in __construct() parameter.

Run again command,
php bin/magento setup:di:compile
an error will be gone.