This functionality allows you to combine and perform several actions in one time and will be especially useful when performing repeating operations. For example, when you close a Task, you can change the status for several fields of the current, nested or linked entity.
You can customize the color and location of the button, as well as the access rights and conditions under which it will be displayed.
If you have installed some payment modules, you can connect them to the Process. Then, after starting the process, a checkout window will appear and the process will be completed successfully only after the payment is made (payment module returns "complete" for transaction).