What is the difference between "博览会", "交易会" and "展销会"?
博览会, 交易会 and 展销会 can be used interchangeablely. All of them mean "exhibition". They are synonyms, different only in literal meanings.

The literal meanings are:


  博览会 broad viewing party
  
  交易会 trade party
  
  展销会 display and sales party