I have not set up this thing in my wallet app partly because I do not understand it. I read a little about it on on-line articles, but I still do not understand it. Please can someone dumb it down for me so I understand exactly how it is used and what it does? I read it replaces something called Venmo and also PayPal, but I still do not quite understand it. I know what PayPal is, but I have never heard of Venmo. Thanks.