Google said What is SEO ?

Search engine optimization (SEO) is the process of affecting the visibility of a website or a web page in a search engine's "natural" or un-paid ("organic") search results.

SEO Stands for Search Engine Optimization.

SEO is all about optimizing a web site for Search Engines like google, bing


All major search engines such as Google, Bing have such results, where web pages and other content such as videos, images or local listings are shown and rank based on what the search engine considers most relevant to users (google use algorithms for finding relevancy content).


Search engines perform  and provide several activities in order to deliver search results.

• Crawling
• Indexing
• Processing
• Relevancy Calculation(Algorithms)
• Processing Results
• Retrieving Results 

Crawling

Crawling is the process of gather or fetching all types of web pages linked to a web site. This task is performed by a software, the software known as web crawlers and the most well known crawler is called Googlebot.

Indexing

Search Engines essentially gathers the pages during the crawl process and then creates an index. Search engines index includes information about words and their locations. When you search, at the most basic level, search engines algorithms look up your search terms in the index to find the appropriate and proper pages of the websites.

Processing

When search engines server receives search request from users or developers, The search engine processes. It compares the search query in the search request with the indexed pages in the database(Server).

Relevancy Calculation(Algorithms)

The request search string contains more than one, the search engine starts calculating the relevancy of each of the pages(calculating content and other things) in its index to the search string.

Processing Results

When the request received by search engines server it responses using matching algorithms to find the relevancy results

Retrieving Results 

The final step in search engines activities is retrieving the best matched results. After that its simply transfer to browser.