The "Short Certificate" is a short form of the Certificate of the Grant of Letters Testamentary or of Administration issued by the Register of Wills when the probate process is begun. The Short Certificate confirms that you have been authorized by the Court to act on behalf of the estate. Until you have been to the Register of Wills and begun the formal probate administration process, you do not have the authority to open an estate account or otherwise take any action on behalf of the estate.
A short certificate is proof from the register of wills, that the will has been probated and that you have been properly and legally appointed as the executor. Be careful, because many banks and institutions ask for this even when probate is not needed. For example, if all of the accounts are joint with a surviving person, and/or there is a small account, such accounts can be closed by the joint account holder just with a death certificate, or, can often be paid directly from the bank to a funeral home. Once you do probate a will to get a short certificate, there are many steps that you must take. Get good advice before probating.