While (or whilst) means 'during the time when something else happens'. When can mean the same as while, but when can also refer to a point in time. Compare. during the time something happens.

When should I use whilst?

Whilst is mostly used in British English, though way lesser than while. While can be used as a conjunction, preposition, noun or verb, whereas 'whilst' is used only as a conjunction or adverb. When used as conjunction/adverb, both the words mean during or at the same time as.

What kind of word is whilst?

In standard British English and Australian English, whilst, as a conjunction, is synonymous with although, whereas, but or while. Unlike whilst, while is also used as a noun (as in "rest for a while") or a verb (as in "while away the hours"). The usage of whilst is chiefly British.