Organic traffic is the traffic you get when people follow links from a search engine results page and land on your site. Organic traffic contrasts with referral traffic which comes from links on other sites, and paid traffic, which is traffic resulting from ads. You can boost organic traffic by using content marketing, and by optimizing that content with SEO. Well-optimized content is more likely to get a high search ranking, and attract more clicks and traffic.
Not all web traffic is welcomed. Some companies offer advertising schemes that, in return for increased web traffic (visitors), pay for screen space on the site. There is also "fake traffic", which is bot traffic generated by a third party. This type of traffic can damage a website's reputation, its visibility on Google, and overall domain authority.