What's the difference between National Arts Centre, National Gallery, and National Archives and Library?

I can't dicide where to go, and they sound like pretty similer.
Which one should I go and why??

the National Gallery is your choice...great works of art, and located right downtown overlooking Parliament Hill and the Ottawa river.

The National Arts Centre is also downtown, but only houses concerts, operas, orchestra's and theatre etc. (Unless you know of a specific show you want to see).

The National Gallery is located further west, but really isn't a tourist location.

Enjoy!

If you like art, The National Gallery has fantastic art work.
If you want to see history the National Archives has the Declaration of Independence, the Constitution and the Magna Carter.
If you want to see and research incredible documents, go to the National Library.

National Arts Centre (NAC) is for concerts with an orchestra, plays and shows. the Centre is among the largest performing arts complexes in Canada. It is unique as the only multidisciplinary, bilingual performing arts centre in North America and features one of the largest stages on the continent.

National Gallery:Permanent home of Canada's exceptional national art collection, especially Canadian art.

The National Archives is Canada's memory bank. Here you can discover the story of Canada, not as it is interpreted in history books, but through direct contact with original documents from the past. The Archives' preserves tens of millions of records ranging from personal photographs to official government documents. The National Archives of Canada is open to all researchers, whether professional or amateur. Visitors are also welcome to enjoy the exhibitions