Certification refers to the confirmation of certain characteristics of an object, person, or organization. This confirmation is often, but not always, provided by some form of external review, education, assessment, or audit. Accreditation is a specific organization's process of certification.
One of the most common types of certification in modern society is professional certification, where a person is certified as being able to competently complete a job or task, usually by the passing of an examination and/or the completion of a program of study. Some professional certifications also require that one obtain work experience in a related field before the certification can be awarded. Some professional certifications are valid for a lifetime upon completing all certification requirements. Others expire after a certain period of time and have to be maintained with further education and/or testing.
Certifications can differ within a profession by the level or specific area of expertise to which they refer. For example, in the IT Industry there are different certifications available for software tester, project manager, and developer. Also, the Joint Commission on Allied Health Personnel in Ophthalmology offers three certifications in the same profession, but with increasing complexity.