The Process of improving the volume or quality of traffic to a website from search engines through "Natural"(Organic and Alorithmic) search results. Main goal is to make websites to get indexed by search engines. Obviously, it is virtual thing to be done by every new companies to survive in the field.
Difference between seo and sem
SEO - The art of making the website to top position in search engines and get the enough visitors traffic for the websites.
SEM - Using of different SEO techniques to increase the sale and profit of the company is defined as search engine marketing