What is SEO?
SEO is search engine optimization or optimizer is a collection of techniques applied to optimize our site so that it ranks well in SERPs (Search engine result pages) like Google, Yahoo, Bing and another major search engines.
Who Do SEO?
They are the Webmaster, SEO Engineer and Website optimizer etc.
What tools do you use for doing SEO?
I use Google webmaster tools, Google Analytics, Open site explorer, Alexa, Website grader etc. But now a days there are so many paid tools are available in market like Seo Moz, spydermate, bulkdachecker etc.