What is Pre-Autorized Debit (PAD)

HI, in my receipt window, i can pay CASH, Cheques, PAD or by Credit Card.  What is PAD? Is it like EFT? I dont always get cheques from clients and when I get an EFT in the paid by Cheque window I enter their cheque number as follow : Trace NO 123555 etc just so I can track it down but maybe I should use the Paid by PAD instead? or is this somehting totally different?