Fixed pattern “×什么（啊）”
In Chinese the pattern “×什么（啊）” is used to brush aside someone's worry or doubt, or to stress how things actually are.
The pattern often carries a tone of:
objection;
reassurance;
“there's no need for that”.
Basic Structure
Verb / Adjective + 什么（啊）
In English, depending on the context:
What are you … for?
What do you mean, …?
Why would you …?
Examples
紧张什么啊，我们都喜欢听你唱歌，你要相信自己。
What are you nervous about? We all love hearing you sing — believe in yourself.
Structure
紧张 + 什么啊
be nervous + what for?
紧张 — to be nervous
什么啊 — what are you … for?
我们都喜欢听你唱歌 — we all love hearing you sing
你要相信自己 — you should believe in yourself
Here 紧张什么啊 is used to take the edge off the listener's worry and reassure them.
胖什么啊，你看起来不胖也不瘦。
What do you mean, fat? You look neither fat nor thin.
Structure
胖 + 什么啊
fat + what do you mean?
胖 — fat
什么啊 — what do you mean, …?
你看起来 — you look
不胖也不瘦 — neither fat nor thin
Here 胖什么啊 pushes back against the listener's “I've got fat”.
急什么啊，马上就到了。
What's the rush? We'll be there any moment.
Structure
急 + 什么啊
to rush / to fret + what for?
急 — to be in a rush / to fret
什么啊 — what … for?
马上 — any moment now
就到了 — we'll be there
Here 急什么啊 is used to calm the listener down.
Quick Rule
Verb / Adjective + 什么（啊）
Meaning: to push back against the listener's worry, doubt or opinion, or to reassure them.
Examples:
紧张什么啊？
What are you nervous about?
胖什么啊？
What do you mean, fat?
急什么啊？
What's the rush?