what is SEO?
To be very precise it is the acronym of SEARCH ENGINE OPTIMIZATION/OPTIMIZER.This is mainly used to improve the credibility and reputation of our website,which if not properly done may bring the worst effect also.But there are many agencies which do the job with accuracy and precision.
Now what an SEO is doing,his prime jobs include content development,structuring of our site,keyword research etc.The term SEO has its relevance when we think about internet business.And i will say the god in the field is google.So in this business all site owners are looking to be indexed by google.The benefit is that, in a google search engine when we search for a topic the results will be displayed according to the “indexing” and site content.
So once our indexing is high it gives us higher chance to come in the search results.And the net effect is “traffic”.The word “traffic” in this context means people visiting our site.All this indexing,traffic,page views etc are inter-related.One thing we must keep in mind,the results coming in the search engine is purely organic,eventhough google allows paid advertisements it has no effect on your site’s presence in the search engine results.
The paid advertisments are shown as sponsered links,you might have noticed them on the right hand top of your results page.One very important thing i read in the google itself is

“We never accepts money to include or rank sites in our search results, and it costs nothing to appear in our organic search results.”

The Strategy
The SEO considers how search engines work and what people search for.Optimizing a website include editing its content to increase its keyword relevance.To be a part of the search world,first google need to know about our site for this we need to submit our site to google,secondly submit a “sitemap”.
There is a process called crawling which is used to gather information about sites,but there are times when a crawler fails to get sufficient info and it is when a sitemap comes to play its role.
SITEMAP
Two types mainly,for user and for the search engine.
Sitemap for user is termed as HTMl sitemap,and those for the search engine is termed as XML sitemap.A sitemap gives the user & search engine a clear picture of our site.
Sitemaps are helpfull particularly when our site has dynamic contents.When our site is new(with less popularity and “back links”).

Hope this thing helps a bit,do come up with comments,i will try helping with what i know in the topic

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3. The Enigma Called SEO
4. Elements Of E-Commerce