“While” is used in verbal sentences, for example:
“While we were talking, someone knocked on the door.”
“Tell me about your day while I wash the dishes.”
Since “were talking” and “wash the dishes” are verbal phrases, you would use “while” to say that something else is happening at the same time.
“During” on the other hand is used with nominal (noun) sentences, for example:
“During the meeting, a coworker of mine fell asleep.”
“Don’t talk during the movie!”
“The meeting” and “the movie” are nouns, and so you use “during” with them. You would never say “while the meeting” or “during we’re talking”. This would be completely wrong. Which one you use depends on what comes after (a noun or a verb).
“Meanwhile” has a similar meaning to “during” and “while”, but it is used alone and is followed by a comma instead of a noun or verb phrase. It’s usually used to connect two sentences. For example:
“My friend was telling me about her day. Meanwhile, I was washing the dishes.”
“I’m going to go to the store now. Meanwhile, can you clean the kitchen?”
There is also a phrase in English which has the same meaning as “meanwhile”: “In the meantime”. Both of these expressions aren’t as common in everday conversation as “while” and “during”.
A side note: “while” can also be used as a noun to express some period of time. It’s not always clear how much time is meant. For example:
“I read the book for a while, but then I got bored.”
An English speaker might interpret that this person read the book for anywhere from 10 minutes to an hour or so.
“I lived in Asia for a while after I got my first job.”
This would be for a few months most likely.
But you can also use “while” with “short” or “long”, for example:
“For a short while” = “for a short time”
“For a long while” = “for a long time”
I hope this helps!