The best way to explain is to start with a couple basics:
Open Bar - Guests aren't paying for their drinks
Cash Bar - Guests are paying for their drinks (they can use card payments too!)
A consumption bar is halfway between the two.
A consumption bar is basically a cash bar where you pick up the bill. This means your bill reflects what was consumed - a consumption bar!
For corporate or ticketed events, a consumption bar can be a great way to control costs while giving back to attendees. Use drink tickets for corporate parties if you want to offer alcohol, but it's not time to let loose. If attendees are purchasing a ticket package to attend an event, tickets are a great way to add value to the package.
VIP guests? Use a consumption bar for your VIP area, or wristbands to indicate VIP guests. VIP experiences are a great way to offer an upgraded experience for sponsors or ticket holders.