A certification of birth is a document that certifies a record of the birth appears in the records of the local office authorized to record records of birth. It may contain a transcription of the entire document or just a portion of it. The certification is not intended to be a complete transcription of the original document. It just confirms that the record is on file.
A copy of the certificate of birth is usually an actual copy of the birth record. From the standpoint of genealogical research, it’s the preferred item to request.
The image contains part of the certification of birth and birth certificate for my late grandmother. The certification of birth contains spellings of her parents’ names that are not what appears to be on the certificate of birth. That’s due to either a transcription error, or in this case that the certification was created from information in a different record–perhaps a register of births that contained a summary of information that appeared on the actual birth certificate.
Issues such as this are why it is crucial to indicate in a source citation exactly what document is being cited. In this case, I need to see if there is a separate register of births for the time period when my grandmother was born. The birth number on the certification of birth is not the number that appears on the certificate of birth.