Whipped cream chargers are small, pressurized cylinders of nitrous oxide gas. They are used with whipped cream dispensers to easily create whipped cream. The basic process involves puncturing the small pressurised canister (the Cream Charger) and allowing the gas to combine with the cream under pressure within the dispenser.
Whilst in the dispenser the the nitrous oxide gas is forced to dissolve into the cream - in much the same way that the fizzy bubbles of carbon dioxide are dissolved into the coke or lemonade. Whilst within the dispenser then the mixture is inactive and inert.
Upon release from the dispenser then the gas is free to expand - and as it does so then it inmates the cream. The amount of whipped cream you get from a single cream charger can depend upon a number of factors, such as the temperature and the type of cream -but you can generally expect to get about three times the volume of cream you started with. This compares with an increase of about 50% when you use a traditional whisk to create whipped cream.