The term you're looking for is "at-will employment." Without an employment contract specifying otherwise, both the employer and employee are generally free to end the employment relationship at any time, for any reason.
Some key points about at-will employment:
• At-will is the default employment relationship in most U.S. states. However, some states provide additional protections for employees.
• There are some limits on an employer's ability to fire an employee - they cannot terminate for illegal reasons like discrimination based on race, gender, age, disability status, etc.
• Employees can quit at any time, while giving reasonable notice, without the employer having legal recourse.
• A contract specifying a fixed term of employment or requiring cause for termination overrides the at-will relationship.
• Severance packages and other benefits may be negotiated when ending an at-will employment relationship. But they are not legally required.
So in summary, without a specific contract, employers and employees have flexibility to end the relationship at any time through a process of resignation or termination, consistent with the legal concept of at-will employment.
Hope this helps! Let me know if you have any other questions.