This converter decodes URL-encoded string (percent-encoded characters). Example of percent-encoded string you can often see in your browser, like in this link: http://en.wikipedia.org/wiki/Percent-encoding#Percent-encoding%5Fin%5Fa%5FURI
Converter supports not only reserved characters (special characters like slash, parenthesis, etc.), but also unicode characters - percent encoding uses UTF-8 encoding for these. Example can be seen below in the input field.