Training involves an expert working with learners to transfer to them certain areas of knowledge or skills to improve in their current jobs. Development is a broad, ongoing multi-faceted set of activities (training activities among them) to bring someone or an organization up to another threshold of performance, often to perform some job or new role in the future.
Training and development can be initiated for a variety of reasons for an employee or group of employees, e.g.: 
1. When a performance appraisal indicates performance improvement
    is needed
2. To "benchmark" the status of improvement so far in a performance
    improvement effort
3. As part of an overall professional development program
4. As part of succession planning to help an employee be eligible for a
    planned change in role in the organization
5. To "pilot", or test, the operation of a new performance management
    system
6. To train about a specific topics such as communications,
    computer skills, customer service, ethics, human relations,
    quality initiatives, safety, etc.

Numerous Benefits can be derived from this process: 
1. Increased job satisfaction and morale among employees
2. Increased employee motivation
3. Increased efficiencies in processes resulting in financial gain
4. Increased capacity to adopt new technologies and methods
5. Increased innovation in strategies and products
6. Reduced employee turnover
7. Enhanced company image e.g. conducting ethics training (not a good
    reason for ethics training!)
8. Risk management, e.g. training about sexual harassment, diversity
    training, etc.