A more thorough explanation:

Express Authority

Express authority is a legal term used in agency law. It refers to the power given to an agent by a principal to act on their behalf. This power is explicitly granted by the principal, either in writing or through clear and express oral instructions. When an agent has express authority, their actions can legally represent the principal and even bind them in a contract.

• An agency agreement between a real estate agent and a homeowner gives the agent express authority to sell the homeowner's property. The agent can legally represent the homeowner in negotiations and sign a contract on their behalf.
• A company hires an advertising agency to create a marketing campaign. The advertising agency has express authority to make decisions about the campaign and spend the company's money on advertising.

These examples illustrate how express authority works in agency law. In both cases, the principal (homeowner or company) explicitly grants the agent (real estate agent or advertising agency) the power to act on their behalf. This means that the agent can legally make decisions and enter into contracts that represent the principal. Without express authority, an agent would not have the legal power to act on behalf of the principal.