两个术语的区别在于agency by estoppel ( “表见代理”)(也称为 agency by operation of law, apparent agency 或 ostensible agency) 并不存在真正的代理关系（actual agency)，即委托人和代理人之间并无代理协议存在，只是因委托人的行为让第三人合理地认为他与代理人之间确有代理关系，且第三人因此种确认作为且受到伤害，此时由法院依据法律推定成立而委托人不得否认的一种代理关系[1]。相比之下，agency in fact ( “事实代理”)所表示的代理关系则是由委托人和代理人经协议事实确立的，其与前者正好相对[2]。
 
[1 ] "An agency created by operation of law and established by a principal's actions that would reasonably lead a third party to conclude that an agency exists. ” Cf. Bryan A. Garner, Black's Law Dictionary, 7th edition, at p. 62，West Group (1999).
[2] “An agency created voluntarily, as by a contract. Agency in fact is distinguishable from an agency relationship created by law, such as agency by estoppel. ” Id. at p. 62.