Organic traffic generally refers to non-paid traffic, Traffic includes traffic from:

Search engines like Google, Bing and Yahoo.
Social media sites like Twitter, Facebook and Pinterest. reddit, livejournal
Referral traffic from other sites - visitors arriving at your site after clicking on a link on another website.
Direct traffic - someone typing in your URL into a browser.

When the internet user's find some task on google or any search engine then they put a special word for searching so the search engine gives a lot's result for it and the internet use click on your website to their keyword and open your website its call as organic search.

Organic traffic is the opposite of paid traffic, which defines the visits generated by paid ads. Visitors who are considered organic find your website after using a search engine like Google or Bing, so they are not “referred” by any other website

"Organic traffic" is traffic that comes to your website as a result of unpaid search results.

Organic traffic is the opposite of paid traffic, which defines the visits generated by paid ads. Visitors who are considered organic find your website after using a search engine like Google

Organic traffic is direct traffic from via search engine or website.

Organic traffic is a traffic that came from the search results.

The term "organic traffic" is used to refer to visitors who landed on your site due to unpaid ("organic") search results. ... Visitors who are considered natural visitors find your site after using a search engine like Google or Bing, so no other site will "recommend" them.