Communicative function：exchange business information between related parties.
交际功能：相关各方之间交换商务信息。
Record‑keeping function：keep permanent records; for reference and dispute evidence.
记录存档功能：永久留存记录，供查阅，可作为纠纷证据。
Promotional function：promote goods/services; attract customers; build corporate image and business relations.
促销功能：推销产品服务、吸引客户、塑造企业形象、维系业务关系。
Legal function：can be legally‑binding documents under certain circumstances.
法律功能：特定情况下具备法律约束力。