Employee retention refers to the ability of an organization to retain its employees. Employee retention can be represented by a simple statistic (for example, a retention rate of 80% usually indicates that an organization kept 80% of its employees in a given period). However, many consider employee retention as relating to the efforts by which employers attempt to retain employees in their workforce. In this sense, retention becomes the strategies rather than the outcome.
In a business setting, the goal of employers is usually to decrease employee turnover, thereby decreasing training costs, recruitment costs and loss of talent and organisational knowledge. By implementing lessons learned from key organizational behavior concepts employers can improve retention rates and decrease the associated costs of high turnover. However, this isn't always the case. Employers can seek "positive turnover" whereby they aim to maintain only those employees who they consider to be high performers.
Herzberg's theory 
An alternative motivation theory to Maslow’s Hierarchy of Needs is the Motivator-Hygiene (Herzberg’s) theory. The theories have overlap, but the fundamental nature of each model differs. While Maslow’s Hierarchy implies the addition or removal of the same need stimuli will enhance or detract from the employee’s satisfaction, Herzberg’s findings indicate that factors garnering job satisfaction are separate from factors leading to poor job satisfaction and employee turnover. Herzberg’s system of needs is segmented into motivators and hygiene factors. Like Maslow’s Hierarchy, motivators are often unexpected bonuses that foster the desire to excel. Hygiene factors include expected conditions that if missing will create dissatisfaction. Examples of hygiene factors include bathrooms, lighting, and the appropriate tools for a given job. Employers must utilize positive reinforcement methods while maintaining expected hygiene factors to maximize employee satisfaction and minimize retention.
See also 
- Breaugh, James A., and Mary Starke. "Research on Employee Recruitment: So Many Studies, So Many Remaining Questions." Journal of Management (2000): 305-434. Web. 12 Mar. 2011.