To get full information, we have to go back to 2011. Firstly when google analytics newly formed, the site owners quickly get the user information. They could see which keywords were attracting users to their site, In organic search reports, and how user behavior varied between different keywords.
But this is the story of before October 2011. In 2011 everything was changed when Google started encrypting search data. The reason behind to make this change is to make the search more secure. Now, your GA account shows up to 99% of the keywords you rank for as “not provided.”
But there is a way to find out the keywords if you are not able to see them on analytics. You have to merge you google analytics account with GSC, i.e., Google search console. There you can quickly get the keywords that are not shown on analytics.
There is another way through which you get the landing pages of not provided keyword. But here you can only get the ranked pages you are unable to get the search term on which these pages ranked.
Simply Go to Google Analytics > Acquisition > All Traffic > Channels > Organic Search. Here you get Not provided a keyword
Next, click on the not provided keyword here. You get the secondary dimension tab just upside the keyword tab, click on it. Scroll down and select the Landing pages option and get the pages on which users visit.
Just check it out which pages are coming in not provided keyword. You can also see the various metrics through secondary dimension tab like source/medium, behaviour, campaign, social, time, users, and so on.