Internet marketing is a type of marketing that uses internet as its primary tool for advertising goods and services. Internet marketing can be divided into the following categories:

search engine optimization or SEO
social media marketing
e-mail marketing
referral marketing
content marketing
native advertising
SEARCH ENGINE OPTIMIZATION
Search engine optimization or SEO is a complex of methods that makes it easier to find a particular website via search engines. The better the SEO of a page, the higher is the rank it achieves in the list of search engine results. Nowadays, when people mostly use internet to search for goods, SEO is an essential marketing tool. Search optimization also allows ensuring that a particular website is mostly shown only to those who are interested in what it offers. In other terms - the website will be most visible to its potential clients. Thus, e.g. a website about web design development will be mostly visible to those interested in web design, not interior or landscape design.

SOCIAL MEDIA MARKETING
Social media marketing is a type of marketing that uses social media to advertise information about a certain product or service. Social media marketing aims at attracting the attention of users and motivating them to to share the information, thus including more and more of the target audience. It is important that the information encourages to read and discover more about the company and its services. Social media marketing also has a significant advantage - it allows users to directly express their opinion about the information. Thus, a company receives trustworthy information about what its target audience thinks concerning a certain service, product or idea.

http://www.arteqo.com/en/marketing/internet-marketing/