Level 1

What is the difference between an ACH payment and an echeck?

I'm new to Quickbook payments. I have been billing customers via email and allowing them to pay via ACH on their own. I went into Quickbooks payments today and saw that I can get authorization to run an echeck on their behalf (with their approval, of course). What is the difference between that and an ACH? Is it just faster because I can process it faster than waiting for the customer to pay or does it actually reach the bank faster? Is there an advantage of one over the other?