Spider crawler indexer search engines

I interest to know how search engine works since I wonder how google and yahoo search engines can do that. It is may not complete component of search engines since I just know some stuff and You may already familiar with them
There are some search engines components that I will listed. Here they are:

Search engine Spider
This is the program that search engine use to download web pages just like a web browser and works directly with the underlying HTML code of the page.

Search engine Crawler.
This is the program that search engine use to finds all links on each page. It is use also to determine where the spider should go to other page.
The crawler follows these links and tries to find new pages or new website that not recorded yet at search engine..

Search engine Indexer.
After a website had spider and crawler it is time search engine indexer to analyzes website component such as text,header,tags etc

Search engine Database.
This is the storage area for the data that the search engine downloads and analyzes websites or document. Again I just wonder how big a server that owned by yahoo and google to saved those data.
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Search engine Results pages.
This is the result search engine pages. It determines which pages match a user's keyword and this is done according to the page rank. While about page rank I will discussed later.

Search engine Website.
This is search engine website that we use regularly To input keyword that we interest in and then bring to us a result pages.