Hello qurashi , Actually keywords are the phrases or words which we use to search out anything using search engines. For example you want to rent a car and searched using "car rental" in google. Here "car rental" is the keyword for search out car rental services. Optimizing for keywords means optimize the site content for search engine for single or multiple specific keywords. if anyone ask you which thing people search most in google or yahoo?
Keywords run the ENTIRE SHOW my friend. Every click. "keywords" is also one word...enless you're already outsmarting all of us and optimizing this thread for "key words"
It depends upon the niche, You are having site related to casinos, poker games and online and internet gambling, And you want to use keyword related to real estate and Seo or web design industry won't match... Select yr niche first than take help from keyword suggestion tools.