What is SEARCH ENGINE MARKETING?

The search engine marketing company concerned in the business of ranking sites for search engines like Google, yahoo MSN etc, - Everyone thinks there is a lot of difference involving SEO ( Search engine optimization ) and SEM ( search engine marketing ).But the truth there is only a thin line between SEO and SEM.
As per statistics over 85% of all up-to-the-minute visitors to a web site originate from major search engines such as Google, Yahoo, AOL and others… It is very essential that every site ensures that their search engine exposure help their visitors (potential customers) to find them. There are 2 distinct factors involved when it comes to search engines and their algorithms; they are on page factors and off page factors.