Agency law is concerned with any "principal"-"agent" relationship; a relationship in which one person has legal authority to act for another. Such relationships arise from explicit appointment, or by implication. The relationships generally associated with agency law include guardian-ward, executor or administrator-decedent, and employer-employee.
The law of agency is based on the Latin maxim "Qui facit per alium, facit per se," which means "he who acts through another is deemed in law to do it himself." Agency, in its legal sense, nearly always relates to commercial or contractual dealings.