Affidavits in Ontario require that you swear or affirm an oath stating that the information is true in the presence of a commissioner of oaths. A notary public also has all of the powers of a commissioner for taking affidavits, therefore, either a notary public or commissioner of oaths can witness your oath and signature. This can be done either in the physical or virtual presence of one of these individuals (doing this by a zoom call is acceptable in Ontario). Since you are making a legal oath testifying to the best of your knowledge that the facts in it are true, affidavits for use in court require a commissioner of oaths’ signature. Foreign embassies and Canadian credit unions, banks, or financial institutions often ask for notarized or commissioned affidavits for the same reason.