Upfront cash typically refers to Rumble offering you a set amount of money "upfront" and in turn they get to use your video and make money with it. If it doesn't make them the amount they paid you then it was a good deal. If it goes viral and you only get what you were initially paid, you may wish you had taken the exclusive route in licensing your video to Rumble.
We offer upfront for Video Management as well (in some unique cases). It means that we pay the creator cash "upfront" (ahead of actual earnings). We take the risk to give the creator cash before we know how it will perform. If the video performs badly, Rumble ends up losing. If the video performs well, the upfront amount gets subtracted from the total revenue and the remainder is paid out (only for Video Management).
Upfront means exactly what it says Money paid ahead of time.
I got $200 upfront cash for Video Management of a video of my calf cramping (it's like nothing you've ever seen). I immediately tried to cash out the upfront payment, and after a couple easily resolved SNAFUs, the money cleared, and has been deposited in my paypal! This is still the first month, and it's already generated an additional $100 in revenue... I LOVE rumble! I can't wait for other horrible things to happen to me so I can profit off of them hahaha