The basic difference between SEM and SEO is that in SEM the quality of traffic to a particular website/portal is increased by payment methods and in SEO, the traffic is by natural or organic or un-paid means. The technical terms that are used in SE marketing are “paid inclusion”, “paid placement” and “contextual advertising”. All these three forms of internet marketing are used simultaneously to increase the visibility of your website when a user searches for the particular phrase/word/sentence related to the content of your website in that search-engine.