A partnership is a legal relationship between persons who have agreed to carry on a business together with the objective of making profits. The law considers each member of a partnership to be an agent of the other members.
A company is an artificial person. Although it has its own legal existence, it cannot itself perform any acts. It must act through the agency of natural persons. The directors of companies (and some other officers of a company) are normally empowered to act as the company's agents.