Tableau public is the free version that doesn't connect to as many data sources as the personal or professional versions, but it's more than capable for most work. It can read data from text (CSV) files and Excel files which you'll be using in this course. Also, you can't save to workbooks on your computer, but instead, save to a public workbook.
However, Tableau desktop is the paid version which allows you to save locally and work with more data sources and save the files on a local server.