What is a Reduction in Force (RIF)?

A RIF, or layoff, is the temporary suspension or permanent termination of employment for an employee or (more commonly) a group of employees for business reasons, such as the decision that certain positions are no longer necessary due to a business slow-down or interruption in work.
Originally the term "layoff" referred exclusively to a temporary interruption in work, as when factory work cyclically falls off. However, the term has also been used to describe the permanent elimination of positions as a cost-cutting measure (or for other reasons).
Euphemisms are often used to "soften the blow" in the process of firing and being fired, including downsize, rightsize, smartsize, workforce reduction or workforce optimization, simplification and reduction in force (also called a "RIF", especially in the government employment sector).
Additional terms are also used:

• Mass layoff implies laying off a large number of workers.
• Attrition implies that positions will be eliminated as workers quit or retire.
• Early retirement means workers may quit now yet still remain eligible for their retirement benefits later.

Finally, while firings imply misconduct or failure, lay-offs imply economic forces beyond one's control.

source: Wikipedia (edited)