If the country of intended use isn’t a member of the Hague Convention, documents can receive an Authentication certificate from the same Secretary/Department of State instead. An Authentication performs the same duty as an Apostille. Note that unlike Apostilles, which typically require no further legalization, Secretary of State Authentications may require further authentication by the U.S. Department of State in Washington D.C. and possibly even Embassy or Consulate Legalization before being sent overseas.
If the country of intended use isn’t a member of the Hague Convention, some documents may require another step in order to obtain Embassy or Consular Legalization. Embassy Legalization (AKA: Embassy Authentication, Embassy Certification, Consular Legalization, Consular Authentication, Consular Certification, Consulate Legalization, Consulate Authentication, Consular Certification) isn’t common but some countries may require you to do so before turning your documents in. Although Consulates, which are smaller versions of Embassies may authenticate or legalize your certified documents, in some cases your documents may only be legalized by the permanent diplomatic mission of the Country’s Embassy located in Washington D.C.