a grammatical question?

Question

What is the difference between when and while?
i was taught that " progessive tense+ while+progessive tesnse"

"when" can not be followed by a progessive tense clause
(but i still see many sentences like that)

is it correct

Answer 1

You have learned it correctly. However, languages are alive and can change in time. Just like we used to use "shall" with the first person, and "will" with others. Nowadays we use will with all.
Grammatically, you should use "while" with a progressive tense.
e.g. He walked in while I was watching TV.
When he arrived, I was watching TV.

Answer 2

yes it is correct