Due to the difference in the power supplies of varying countries, the designed voltage rate of certain appliances also differ. Travelling to a different country, you may come across the opportunity of using a different voltage from their usual one. It may result in having to use a Step Up/Step Down voltage converter or a travel adaptor.
The most common power supplies are 110v and 120v for those in the US, Canada, etc. and 220v, 230v, and 240v for those in Europe and Asia. Depending on the appliance, if the voltage is too high, it will draw a lot of current that might burn it out and if it is too low, it will draw insufficient current that might end up not performing to its rating.
Using a 110v device and plugging it to a 220v outlet, it might burn out very quickly. It will last a bit longer if it was the other way around however, if it was an AC mechanical drive, it may fail to start or take more than what it is designed for and burn out.
Using devices with the right voltage for your outlets can be the difference between its potential to work properly and one that might burn out or deliver inconsistent results.