difference between sentences

[fugitivemind]

What's the difference between those below 2 sentences.

1. What you did?
2. What did you do?

any of the answer/opinion are hearty accepted and welcome.
I'd really appreciate it.

best regards

[birdeen's call]

The second sentence is correct. Where did you see the first one? I'm not sure if I've ever heard it.

[fugitivemind]

There are lots of similar sentences in google.

[Barb_D]

"What you did" is fine for a noun phrase.

What you did was very generous.
I still can't believe what you did for us.

It's not at all grammatical as a full sentence in the form of a question.

[birdeen's call]

"You did what?!" is a possible utterance. When people say it, they often look like this or like this. It's not the most polite thing to say.

[fugitivemind]

"What you did" is fine for a noun phrase.

What you did was very generous.
I still can't believe what you did for us.

It's not at all grammatical as a full sentence in the form of a question.

For Example,

"The system has failed Boby. What you did? I thought you did something wrong."

So, doesn't above sentence make sense?

[Barb_D]

Not really, no.

[fugitivemind]

Not really, no.

If you don't mind could you please correct the above sentence.

[Barb_D]

What is the middle part saying?

I can't correct it until I have a better sense of what it is trying to say.

[fugitivemind]

"The system has failed Boby. What you did you do? I thought you did something wrong."

Now is it correct ?