Legalization (authentication) is a essentially a stamp the Chinese consulate/embassy affixes to your documents to certify your Canadian documents for use in China.

Here are the steps to legalize your documents in 2020:

Most documents, including university degrees and criminal background checks, must first be notarized by the local public notary. However, Canadian marriage certificates, birth certificates and death certificates don’t. A notary will stamp and notarize your document or make an official notarized copy of your document.
Once your document is notarized, it needs to be authenticated/certified by the provincial authority responsible for authentication (listed below). They will affix an authentication certificate to your document.
Once your document is authenticated by the provincial authorities, it is ready to be legalized by the Chinese consulate. Send the documents to the Chinese Visa Service Centre, which will then forward it to the consulate for legalization (which the Chinese consulates/embassy call authentication, though this is actually step 2).

These are the documents that the Chinese Visa Service Center in Toronto asked to be submitted for legalization (authentication) by the Chinese Consulate

The authentication application form
A photocopy of your passport information page
A personal statement stating the nature of the emergency, dated with you signature
An invitation letter from your employer that states the emergency
The document to be authenticated