Accreditation is a process in which certification of competency, authority, or credibility is presented.
Organizations that issue credentials or certify third parties against standards are themselves formally accredited by accreditation bodies.
Hence they are sometimes known as "accredited certification bodies". The accreditation process ensures that their certification practices are acceptable, typically meaning that they are competent to test and certify third parties, behave ethically and employ suitable quality assurance.
In everyday language the terms Accreditation and Certification are often used interchangeably. However, these terms have specific meanings.
ISO’s formal definition of accreditation is “third party attestation related to a conformity assessment body conveying formal demonstration of its competence to carry out specific conformity assessment tasks.” (ISO/ IEC 17000:2004)