The Tableau Desktop could be downloaded for free for a trial period of 14-days after which you need to pay the licensing fee for continued usage. Whereas, Tableau Desktop is free for full-time students. Tableau Public is another one that is free and is used to connect to a spreadsheet or file and generate interactive data visualizations for the web. Meanwhile, Tableau reader is also free that allows you to interact with visualizations built in Tableau desktop.
Have a look at Intellipaat’s Tableau training course, which is designed to make you a professional in Tableau through instructor-led and self-paced video modules combined with guided projects and exercises to help become a certified professional.