There is a long history to this. At this point you should ignore the "Acquisition / Channels / Organic Search" report. It isn't useful anymore.
So why do they even have a report that isn't useful? Google analytics should just remove it now, but several years ago it was a great report with good data. It used to be that when a user clicked from the search engine to your site, your site would get a referrer URL that included the search term:
Google Analytics and other web stats would parse these words out and tell you which searches to your website were most popular.
Then Google realized this wasn't great for them:
- Users expected more privacy. They didn't expect sites to know what they searched for to get to them.
- ISPs were aggregating and selling data about what their users were searching for by mining non-encrypted HTTP traffic for Google search URLs
- Because webmasters had lots of insight into the keywords, some sites were building pages just to target keywords but not be all that helpful to users
Google started using technical tricks to hide this information from the referrer. Through redirects, HTTPS, and no-referrer tagging, Google now sends a referrer that removes the search term from the URL:
Google Analyitics shows keywords for such URLs in the report as "Not Provided."
Now Google isn't providing any keywords in the referrer and that report is almost all not provided keywords. Totally useless and should just be removed.
For webmasters, Google does make some keyword data available through Google Search Console. That data can be linked to Google Analytics, as you appear to have already done. That data is in the "Acquisition / Search Console / Queries" report. That data is not based on referrers, rather it comes directly from Google. It is based on clicks that Google tracks on the search results itself. So the differences to the other report are:
- The data is Google only. The other report will have data mixed from other search engines such as Bing and Duck Duck Go.
- The data is aggregate only. When data was in referrers, it was possible to tie search terms to particular users.
- The data includes "impressions" which is the number of times your site appeared in the search results for that term, even when users didn't click on it. That impression data is not available through the report based on referrers.
- The data has the long tail removed. Google no longer allows webmasters to see queries that don't have at least several searches per month.