This step is required if you have a light that runs off a different mains voltage.
As I live in the UK our outlet voltage is 230VAC but my wall washer was from the US and required 110VAC. This was not a big problem to get over due to the invention of the transformer.
If you require a different voltage you can use a simple step up or step down transformer. Here are a couple of thing to remember if you need to buy one:
Make sure that you get a step down if you live in the UK and want to use a US lamp and a step up if you live in the US and have a UK lamp (quite unlikely).
Make sure the Power consumption or VA (Watts) of the your wall washer is less than the recommended max wattage of your step up or down transformer
Be sure that you get one with the right plug and socket for you country and lamp
The Elemental LED 64 PAR RGB wall washer uses around 55W so I purchased a step down transformer that was advertised as 100W however it only said 70W on the safety label....so be careful when buying online