EXCLAMATIONS

A sudden cry or remark, especially expressing surprise, anger, or pain:Meg gave an involuntary exclamationan exclamation of amazement

The grammar frame of this sentences is dependent if the sentences is on plural or singular:

What + a(n) + (adjective) + singular countable

-What a wonderful world 

-What an idiot 

What + (adjective) + uncountable/plural noun

-what beautiful breaking down 

How + adjective + adverb

-How smart she is