How IRCC defines it
A certified translator is one whose credentials a Canadian government body can verify, because they belong to an official provincial or territorial association. IRCC defines the term precisely: “A certified translator is a member in good standing of a provincial or territorial organization of translators and interpreters in Canada.”
For super visa and other IRCC applications, this matters whenever a document isn’t in English or French.
Why the certified route is simpler
The practical advantage is packaging: a certified translator seals or stamps the work, and “The seal or stamp will have a membership number that we can verify,” so no separate sworn statement is needed.
That is the main difference from an uncertified translator, whose work must instead be backed by an affidavit. If you have a choice, the certified route usually means fewer moving parts at submission time.