Agency is a relationship based on an agreement authorizing one person, the agent, to act for another, the principal. For example an agent may negotiate and make contracts with third persons on behalf of the principal. Actions of an agent can obligate the principal to third persons. Actions of an agent may also give a principal rights against third persons.
An agency can be created for the purpose of doing almost any act the principal could do. However, there are some acts that must be done in person and cannot be done by an agent. Examples would be: testifying in court for another individual, making a will, and voting.
A general agent is authorized by the principal to transact all the affairs of a particular kind of business. For example, a person appointed as manager of a store is a general agent.
A special agent is authorized by the principal to handle a particular business transaction or perform a specific act. For example, a specific power of attorney appointing an agent (attorney-in-fact) to sell a particular piece of real estate or a certain car would be the appointment of a special agent.
A universal agent is authorized by the principal to do any act that can be delegated to a representative. An example would be giving a person a general power of attorney. This form is such a general power of attorney.