Failure to do so could severely damage or destroy your appliance. A converter must be used to convert the voltage of the supply to match your appliance. You can find this information listed on the appliance manufacturer's label located on the back or bottom of the appliance or in the specification section of the appliance owner's manual. If only the amperage rating is shown, multiply the input voltage by the amperage rating to find the wattage rating. What adapter is needed where is often a lesson in past colonialism.
Many countries have a multitude of electrical outlet configurations, some to ridiculous proportions.
Usually they are island nations or countries which saw a rapid influx of wealth as their infrastructure was developing, i.e. many Middle Eastern countries. To be safe, you should take all required. This difference in frequency may cause the motor in your 50Hz appliance to operate slightly faster when used on 60Hz foreign electricity. This frequency difference will also cause analog clocks and timing circuits that use AC as a timing base to keep incorrect time. Most modern electronic equipment including battery chargers, computers, printers, stereos, tape and CD players, VCRs, etc will not be affected by the difference in frequency.