What is the difference between keywords and meta keyword?

Meta keywords are the ones you use in the header area of your website. Keywords can be anywhere in your webpage. Hope that helps.

I am completely agree with Mr.Oliver ,Meta keywords are those keywords which are used in header area of the website and keyword is a simple key phrase which can be used anywhere in the website while developing the website. Keywords are most important part of the website as far as SEO is concerned because keywords drags the visitors to a website and if you are not targeting a correct keyword then it might be possible that you will lose some of your visitors. So while you are going to choose the keywords then always choose that keyword which has high traffic and low competition because it is easy to chase that keyword in lesser effort. Source:-http://www.tisglobaluk.co.uk/seo-company-uk.html

You should start by reading https://northcutt.com/wr/google-ranking-factors/ to understand the role keywords play in the success of your site in ranking for Google. Keywords are one of, if not the, most important aspects of any SEO strategy. Your question is very generic and going to invite a lot of speculation. Keywords should be used in several places on a webpage. A keyword meta tag is a list of keywords used on a page, but this meta tag is not used by Google in determining search results. It is, however, used by smaller search engines and vertical search engines. The meta tag is also useful for a website's internal search program, for tags used with link submissions, and for internal inventory purposes.