As of today, there are three types of certification:
Power-of-attorney that is issued to execute one or several acts, or authorizes the agent to fulfill maximum completeness of actions.
Copy certification by document custodian is a widely-spread procedure. A copy of your identification document can be requested at the place of your work or studies, as well as in different law enforcement agencies, social or pension agencies, and banking /crediting institutions.
Any person, even not the owner of the document copy, can apply for notarization. The only exception is a passport copy. All the documents to be used abroad must be notarized and legalized with the apostille (for the country that is a party of The Hague Convention of October 5, 1961), translated, and laced (binding)