Principal-agent relationship: agents bind principals, owe fiduciary duties and entitlement to indemnity, distinct from sale. An agent can bind the principal and alter the principal's legal relations with third parties while remaining subject to a lesser degree of control than a servant; agency creates a fiduciary duty requiring the agent to account to the principal, entitles the agent to remuneration, and obliges the principal to indemnify and reimburse liabilities and expenses incurred in the reasonable performance of the agency. By contrast, a purchaser in a sale acquires title, and contractual restrictions do not by themselves convert a sale into an agency.