A search engine is a (usually web-based) system for searching the information available on the Web. Some search engines work by automatically searching the contents of other systems and creating a database of the results. other search engines contains only material manually approved for inclusion in a database, and some combine the two approach.
 
The software tool that helps users find Web pages and web sites that relate to one or more key words that they have typed in. The visitor to the search engine may type into a "search box" the term, keyword or phrase that are wanting to find information about - and the search engine then returns a list of web pages and websites which it feels relate to the searched keyword. If you sell for example "helium balloon gas" then you would hope that if a visitor has searched for "helium balloon gas" then your website will be one of the first to be listed.

Some engines - often termed search engines are actually "Directories" - one such example is the Dmoz (Open Directory) engine. These directories are reviewed and categorised by human editors, not spidered (automatically checked) by computers. It is therefore important to ensure that your web site is entered into these directories correctly.

Search Engine Optimisation (SEO) is the process of increasing the likelihood of a document or web page being returned high up in the lists which search engines display. - the process of making your website search engine friendly to make it rank higher in the search engines.
 
Search engine optimisation (optimisation) primarily involves making skilled adjustments to your content and code so your site is seen as being relevant

You might have a great looking website, but what use is that if you get no visitors? 80% of people using the internet find websites via the search engines. Website optimisation is crucial for both ensuring the pages of your website are indexed by the search engines and ensuring that your site is favourably ranked and therefore found by visitors seeking your products and services. 

The internet is an enormously powerful marketing tool, but your web site is only going to be effective if people actually visit it. The way people use the internet is heavily dependent on the resources offered by search engine technology - over 80% of people turn to a search engine as their first means of finding what they're looking for on the web.
 
Since all the search engines use different rules and algorithms to ascertain which websites they feel bear most relevance to particular keywords they often return different listings. As the search engines are continually changing these "rules" it is of utmost importance that your website is optimised to reflect these rules. It is also necessary to alter the web site optimisation from time to time in order take advantage of any recent changes in the way the search engines work.

Pay per click (PPC), also known as pay per bid or paid listings is a service provided by some companies e.g. Google, Overture. The pay per click service allows advertisers to pay for the traffic delivered from the search engine.
 
Pay Per Click (also known as Pay Per Ranking, Pay Per Placement or Pay Per Position) enables you to list your site at the top of the search engine results by advertising on keywords that best describe your product or service.
 
The higher you bid, the higher your advertisement will be displayed in the list. You pay only when a searcher or clicker clicks on your listing to look at your website.
  
You don't pay to list, you only pay for clicks or click through's. This way you only pay for the traffic to your site, there are no other hidden costs.

A specific kind of HTML tag that contains information not normally displayed to the user. Meta tags contain information about the page itself, hence the name ("meta" means "about this subject") Typical uses of Meta tags are to include information for search engines to help them better categorize a page.
 

Meta tags are important for search engine optimisation for a couple of main reasons. The first being that some search engines still use the contents of the keywords and description tags as a factor used to help determine the content of the page. Some search engines use the contents of the description tag to display the snippet of information about the page in their search results page.

There are two ways a search engine can find a website to add to its database. The first and most direct method is to accept submissions from website designers and optimisers. Most search engines have a "submit your URL" section inviting submissions from Internet users.
 
The second, and least obvious method of finding websites is to send a "spider" to follow each and every link on, off, and through a website. New URLs encountered by the spider will be added to the database. In this way, some search engines will grow very rapidly. Thirdly some search engines derive the information for their listings directly from other search engines.

As such, a web host cannot help to improve the rankings. Search Engines will not rank you higher because your site is hosted on a particular web host. However if the server where your website is hosted is often "down" or indeed i your website is slow to load ( as it often the case with "cheap" web hosting deals - when the hosting company place too many websites on a particular server) then yes this can have a negative effect in that when the search engine spiders your website if it is not available or too slow, the spider will simply give up crawling your website and your website wont get indexed in their lists - indeed if your website is down it could result in a search engine de-listing you.