The main difference between both of them is for google ads we have to pay to google for the website then google will put your website in the top of the search result, whereas organic rankings are by the using SEO (search engine optimization) you can place.

your site at the top of the search result.Google ads it can also be explained by if your website is in top of the search result then google will gove you the ads when anyone sees the advertisement at your website you can earn a good amount of money.

Organic ranking is search engine rankings which is not paid, based on your quality backlink the result will be shown for the searched keyword, whereas Adwords are inorganic or paid, it is temporary shown, once your budget is exhausted the ad will be removed from search engine.

Also read : How to create campaign in Google Ads?