Certification is part of testing, inspection and certification and the provision by an independent body of written assurance (a certificate) that the product, service or system in question meets specific requirements. It is the formal attestation or 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. According to the U.S. National Council on Measurement in Education, a certification test is a credentialing test used to determine whether individuals are knowledgeable enough in a given occupational area to be labeled "competent to practice" in that area.

As a rule, certificates must be renewed and periodically reviewed by a certifying regulatory body responsible for the validity of the certificate's assessment methods. The certifying body can be either a state authority or an independent private company. Certificates may even be issued by the companies themselves that use them, primarily as a marketing gimmick, which can be characterized as "cheap talk," meaning a trick that doesn't guarantee trust.

A study conducted by the Certification Board of Computing Professionals (CBCP) showed that the average salary increase for IT professionals who obtained CompTIA certificates was 15%. Similarly, a study by the Project Management Institute (PMI) found that certified PMP® project managers earn on average 20% more than their non-certified counterparts.

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.

Certification does not designate that a person has sufficient knowledge in a subject area, only that they passed the test. This of course apples only to exam-based certifications. Education-based certifications, require that a person completes a course of study that satisfies certain body of knowledge claims to demonstrate that the person has sufficient knowledge in the subject area.^{[citation needed]}

Certification does not refer to the state of legally being able to practice or work in a profession. That is licensure. Usually, licensure is administered by a governmental entity for public protection purposes and a professional association administers certification. Licensure and certification are similar in that they both require the demonstration of a certain level of knowledge or ability.

Another common type of certification in modern society is product certification. This refers to processes intended to determine if a product meets minimum standards, similar to quality assurance. Different certification systems exist in each country. For example, in Russia it is the GOST R Rostest.