At-will employment is a type of employment agreement in which an employee or an employer can terminate the contract at any time for any reason. This means that "just cause" is not required to end the employment arrangement. At-will employment is also known as terminable-at-will employment.
At-will employment is a less binding type of employment than other forms of employment. It offers a lot of freedom to both employers and employees because they can each choose to end the contract if they want. However, the other side of this equation is that either party can be abandoned by the other at the drop of a hat.
At-will employment creates an incentive for employers to hire because they can easily be free of the employee if they feel that they have made a mistake. However, for people looking to obtain longer term positions, the "just cause" approach to contractual agreements may be more attractive since it means they can't get fired without a reason.