Bothe while and whilst have been inthe language for avery long time.while was in use in old english.
Whilst is a middle english development of while.As conjuctions they are interchangeeable in meaning,but whilst has not survived in standard american english.
For ex:
I waited while breakfast was finished.
I waited whilst mugabe delivered what he thought were his pearls of wisdom.
Actually 'while' is older than 'whilst' and both words are still used in British English and are interchangeable, just like 'although' and 'whereas'. Still, the only difference is in the usage of these two words, 'while' is used more commonly in speech whereas, 'whilst' is used mostly in literary compositions and is considered as a formal word.
I hope this helps.
"I am free of all prejudice. I hate everyone equally." - W. C. Fields :)
