Rather than give you literal definition of algorithms I will explain there definition in relation to search engines.
Search engines tend to use software to review and include web sites. Why? Generally because it would cost too much and take too long using humans to review sites. Algorithms are basically rules that have been programmed into their software to review your web site. Each search engines has different algorithms which they change on a regular basis. These algorithms are kept secret however it is possible to work out some of algorithms.
How do you work out current algorithms?
You perform searches on search engines looking at key phrases you are interested in. Visit some of pages at top of results and look at structure of their pages. They have obviously passed algorithm tests so you should be able to work out some of algorithms from pages they have created.
What do you look out for?
If you use Internet Explorer to surf internet, go to VIEW menu and press SOURCE. This will show source code of page including meta tags.
1.Firstly look at meta keywords for that page. You should find keyword you typed into search engine. 2.Then look at title and description. Is that keyword mentioned in title or description? 3.Then go back to your Internet Explorer browser and check in body text for that keyword. Pay particular attention to: a) where keywords are: i) first few words ii) beginning of document iii) end of document or iv) middle of document. b) how many times keyword appears on page. c) is keyword part of domain name for example my domain name is www.bpwebmaster.com and one of my keywords is "webmaster". Now long domain names are available you can even buy domain names with phrases in, such as www.webmastermarketingconsultancy.com and have a phrase of "webmaster marketing consultancy".
Other common algorithms
Do NOT use frames or flash on your home pages. Do NOT use hundreds of keywords. Use phrases rather than just single words because majority of people type in two words or more when conducting a search. Make sure keywords are relevant to that page. Do NOT use same keywords throughout site. Do NOT submit your web site more often than once per month. Do NOT submit more than four pages a week to any one search engine. Do NOT make copies of a page then submit all those copies to same search engine. Do make copies of a page and submit to different search engines. (as search engines have different algorithms you may want to create an optimized copy for each search engine, in other words make slight modifications to page in order to abide by all algorithms of that search engine. But make sure you only submit one copy of that page, rather than submitting all copies). Do NOT use a free domain or sub domain. Try and get reciprocal links on other sites to your web site. Some search engines are rumored to have algorithms that give a higher position to those linked from other web sites. You could buy another domain name and create a page to key pages on your web site. Submit this site to search engines and robots should follow URLs to those pages.