Search Engine Marketing is an Internet marketing techniques that is used to increase the search engine visibility of a website by optimizing it to acquire higher search rank. Search Engine marketing can be considered as a subset of Search engine optimization as the prime focus of both the terminologies is same but the major difference is that search engine marketing is paid feature to attain better search rank.
Google as well as other search engines separates the two types of contents to ensure that there is no biasing in displaying the search results.