SEM ~ Search Engine Marketing

Paid Inclusion This is simply the practice of paying a search engine or a directory to add a site to its database immediately, rather than setting up that site so that it will be found by the search engine spiders on its own. In the case of some search engines and directories, paid inclusion is the only way to get listed. For others, it's presented as an option. If you're willing to pay, your site will be listed sooner. It's also a useful practice if you wish to make frequent changes to your content, because your site will be spidered more often and you will be able to test how changes affect your ranking.

Traditional Ads This involves placing paid advertising on the search engine result pages (SERPs). Normally, these ads appear based on the keywords entered into the search engines, and one is charged based on the number of impressions, i.e. appearances, of the ad. In other words, you pay whether the ad sends anyone to your web site or not.

Pay-Per-Click (PPC) Advertising PPC ads are simple enough to look at. They're text-only. PPC ad campaigns are completely controlled by the advertiser. You decide which keywords should bring up your ads, you write the copy, and you decide how much you want to pay. And, as the name indicates, you only pay for an ad when someone clicks it and is brought to your site. There are two main networks of PPC ads, run by Google and Overture, and each has its own advantages and disadvantages, but in both cases, one should be prepared to spend a great deal of time (and money) monitoring and adjusting such a campaign.