展览, 展会, 展览会, and 博览会 these words have a similar meaning,
or sometimes we use 博物館 as the same meaning as a museum.
展会 is kind of abbreviation of 展览会, in Chinese, we like to cut the beginning and ending of a compound words as an abbreviation.
展览 vs 展览会, you can try to divide to see them, there is only a word 会, which mean a place for displaying some art design, so, you can treat 展览 like this example, I'd like to see "art design" with my friend.
館 or 会 mean a place or a meeting
Hopefully, this explanation can help you. :)