What is the difference between the two types of SEM Pay-Per-Click Marketing and Search Engine Optimization?
The difference between the two types of SEM can be summarized as follows:
Pay-Per-Click Marketing is more like traditional advertising – you pay to be shown in the search engine listings for specific keyword phrases. But unlike traditional media, you don't pay for impressions; you only pay when someone actually clicks on your ad – hence the term "pay-per-click." When you make a 'keyword buy', your listings are shown in the blue area below. These are also known as the paid listings or sponsored links, but are referred to in the SEM
Search Engine Optimization – or SEO for short – is more like public relations. You cannot buy 'publicity' for your site; you have to work for it by undertaking specific techniques and strategies. Generally, these activities include making changes to your website to included targeted keyword phrases and increasing the quality and number of incoming links to your website. When you conduct SEO, you are attempting to get your site listed in the red area below – the unpaid or organic listings

What is Pay per Click?
Pay per click advertising on search engines allows you choose keywords you would like your site to appear for when a search is performed. You decide how much you are willing to pay each time a person clicks on the search results. The more you are willing to pay per click, the higher your site will appear in the results for the keywords you choose.

16. Which Search Engines Allow Pay Per Click Advertising?
There is hundreds of pay per click search engines.
Generally, the larger the pay per click search engine, the more you will have to bid to get to the top for your keywords. This is why it is worth investigating different search engines to find what it would cost to bid on your keywords and how much traffic they draw.
The largest companies in the pay per click industry are Yahoo! and Google. Google is not a pay per click search engine, but it does provide pay per click advertising in text ad boxes to the right of search results it delivers. It also delivers pay per click ads to other content sites.
To find more pay per click search engines, take a look at those listed in the box in the right column of this page.
These pay per click search engines are not as large as Overture and Google, but they are worth a look. As mentioned above, one advantage these search engines can provide is they generally have lower costs per click to rank for a keyword than the larger search engines.
In addition to the general pay per click search engines, you may also be able to find thematic search engines that serve your industry or specifically cater to your target audience.

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