A bailee, also called a custodian, is a person with whom some article is left, usually pursuant to a contract (contract of bailment). The bailee is responsible for the safe return of the article to the owner when the contract is fulfilled. A good example is a parking garage attendant.
An agent is a person who is authorized to act for another...the principal, through employment or contract. An agent can bind the principal by contract or create liability if the principal causes harm while in the scope of agency.
The main difference between the two is that a bailee is not authorized to act for the principal.