The principal-agent refers to the Agency conducted according to the principal's entrustment; the legal agency refers to the agency relationship arising from the direct provisions of the law; the designated agency refers to the agency relationship that occurs according to the designation of the people's court and relevant units. The principal-agent should pay attention to the following problems: 1. Choose the agent carefully. (2) the authorization content should be clear. The name, power of attorney and power of attorney shall be written and signed by the agent. The entrusted matters should be legal.