A translator is someone who translates a document from one language to another. A translator is distinguished from an interpreter who provides live translation of spoken language. A certified translator is one who has be given certification by the government agency, court, or credentialing organization in his or her country, often a member of the Fédération Internationale des Traducteurs (International Federation of Translators), or received one from an educational institution.
In the United States, it is essential to distinguish between a certified translator and a certified translation. Generally, in the United States, a certified translation is a translation that meets certain criteria, but it does not have to be prepared by a certified translator, with the exception of documents used in legal proceedings in at least some jurisdictions. The criteria for a certified translation are the inclusion of three items: the source document or a copy thereof in the original language; the translation; a signed and notarized affidavit attesting that the signee — either the translator or the translation company — believes the translation to be an accurate and complete rendering of the original. In other countries, however, a certified translation is a translation done by a certified translator.
A certified translator has usually passed an exam, as well as undergone education — formal or otherwise — to earn certification. That is not necessarily the end of the certification process. At least for some certifying bodies, continuing education is required to maintain the certificate. In some places, specialization is possible, so you may find certified legal translators, for example.
There are certain types of documents for which a certified translation, and therefore a certified translator, is often required. Many of these are documents that have legal importance. Examples of documents for which a certified translator is often required include birth certificates, adoption papers, immigration papers, licenses and permits, marriage and driver’s licenses, high school and college transcripts and diplomas, and medical records. Other documents that certified translators may handle include patents, contracts, trade agreements, depositions, court orders, affidavits, divorce decrees, wills, etc. Certified legal translators may specialize in one or more areas of legal translation and focus on particular document types.