As in a Corporation, which is a Legal Person, must act on behalf of Agents (employees) to make an Contracts with other Principals (Natural Persons or other Legal Persons) to perform work.
In the Law of agency the Principal is the Accountable party which delegates Authority to an Agent which is the Responsible party for performance of the relationship with the Third-party
In the United States the distinction between independent contractor and employee is an important one as the costs for Organizational Entity to maintain employees are significantly higher than the costs associated with hiring independent contractors, in part due to United States federal government and state requirements for employers to pay FICA (Social Security and Medicare taxes), unemployment taxes, and often Health Insurance on received income for employees.
Likewise, employees are protected from being fired without cause, and if fired or let go for other reasons are entitled to unemployment benefits, whereas independent contractors have neither protection nor entitlement. Employees are also entitled to receive overtime pay for work performed over the 40-hour-per-week standard, whereas independent contractors may work any number of hours (including far above this standard) with no change in pay.
No written agreement or mention in an employee manual is required, though this may be recommended.
HOWEVER, when Original work is created by an independent contractor, then the Copyright law will only qualify as a "work made for hire" and therefore owned by the employer, IF
Computer software, websites, graphic work, and music will often not be considered included in one of the “work made for hire” categories.
An agent is authorized to "to act on behalf of the principal"
A custodian is a holder of an asset for a principal and MAY or MAY NOT Authorized to also "to act on behalf of the principal"