different types of search engines
Although the term "search engine" is often used interchangeably to describe crawler-based search engines, human-powered directories, and everything else, are not all equal. Each type of "search engine", collects and classifies ads into radically different shapes.
Correa-based
Crawler based search engines like Google and Yahoo to compile their lists automatically. That "crawl" or "spider" the web, and people look through your ads. These listings are what make the search engine index or catalog. You can think of the index as a massive electronic file containing a copy of each web page the spider finds. Because spiders searching the web on a regular basis, any changes you make to a website, or links to or from your own website, can affect your position in search engines.
It is also important to remember that it may take a while for a page spidered which is added to the index. Until that happens, is not available for those seeking a search engine.
Search Engine Optimization (SEO) refers to making changes to a web site so you can reach the top positions of search engine specific keywords in organic results.
The results refer to organic search engine results displayed by normal search engines based chain, compared to sponsored results are paid advertisements.
Directories
Directories such as Open Directory relies on human editors to compile their lists. Webmasters submit an address, title and a brief description of your site, then the editors to review it. Unless you join a paid inclusion program, it may take months for your website to be reviewed. Even then, there is no guarantee that your website will be accepted.
After a website in a directory does however, is usually very difficult to change its position on search engines. So before submitting to a directory, spend some time working in their titles and descriptions or hire a professional to submit to directories for you.
Paid inclusion
Most directories offer some form of paid inclusion. Paid inclusion guarantees your website will be reviewed and / or indexed quickly. Note that these search engines usually allow people to file for free, only takes longer.
Pay Per Click (Sponsored Results)
PPC advertising is the name of the ads that appear at the top or right of organic results in search engines. SM services like Yahoo, Google AdWords, MSN AdCenter and allow you to pay to display their ads on its search engine results page. What you pay (supply), together with the click-through rate of ads (CTR) and the relevance of the landing page to determine the ranking of your PPC ads.
Some companies like Red carpet Web Promotion configure and manage PPC campaigns for companies offering many keywords (which can number in the thousands). Contact Red Carpet Web Promotion if this or other web promotion services of interest.
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What are the different types of search engine ? 
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