Tableau Prep is a paid version which offers a trial period for its users to test and experience the capabilities of its software which now comes bundled with tableau desktop in Tableau Creator. After the trial period ends you need to pay and subscribe to use the software, that cleans the raw data and feeds the data source to the tableau desktop.
Learn tableau by taking up the Tableau certification course from Intellipaat which will also help you in getting yourself prepared for the Tableau Desktop Qualified Associate certification exam and will also benefit from Lifetime technical support.
Do have a look at our learn tableau step by step YouTube video from our experts.