This will create a duplicate database and you can do as many transactions as you like. Everything will work as in normal mode (printing, etc.). Once you are finished training, you just Disable Training Mode either by the same step as to activate, or at the bottom of the screen click the Disable Training Mode button. As training mode uses a copy database, nothing has changed in your working copy.
You can also enable training mode on one terminal while you use other terminal(s) for running the business and it won’t affect operations.
If you use V5, Training Mode and Database Tools functionality is included. You can follow the same steps to enable / disable, just you don’t need to install the module first.