We can conclude the following: To emphasize (focus) that an action was in progress at a specific time, use while + a progressive tense (= While I was eating,...) Otherwise, use when + a simple tense. (= When I ate,...) Verbs with while have a duration.

'When' is used to express two single actions that happen simultaneously. 'While' is used to express two continuous actions that happen simultaneously. If you pay close attention, you can see that 'when' and 'while' both express a condition and its results.

So as a general rule, you should use “while” in a clause with a continuous action, using a verb in a continuous tense. Use “when” in a clause with a single action, using a simple past or present tense.

When reflects a general relationship between two events, i.e. at the time or event that one action happens, another also happens. Conversely, While indicates a continuous state, in the sense that when two events take place simultaneously, we use ‘while’.