Traffic can be divided into two main categories: Organic traffic and Paid traffic, but there are more categories and not less important.
Direct traffic: Visitors who visited the site by typing the URL directly into their browser.
Referral: Visitors referred by links on other websites.
Organic Search: Visitors referred by an unpaid search engine listing, e.g. a Google search
Paid :Visits from Paid sources such as cpc, cpm, display, ppc, and more.
Social: Visits from social networks/sites
Unknown: If a visit doesn’t apply to any of the above rules.
Usually, the Search traffic belongs to Organic category as it's "natural" for users to start looking at serch engines.