An astronaut in training for an extra-vehicular activity mission using an underwater simulation environment. The term training refers to the acquisition of knowledge, skills, and competencies as a result of the teaching of vocational or practical skills and knowledge that relate to specific useful competencies. It forms the core of apprenticeships and provides the backbone of content at technical colleges and polytechnics. In addition to the basic training required for a trade, occupation or profession, observers of the labor-market[who?] recognise today the need to continue training beyond initial qualifications: to maintain, upgrade and update skills throughout working life. People within many professions and occupations may refer to this sort of training as professional development. Some commentators use a similar term for workplace learning to improve performance: training and development. One can generally categorize such training as on-the-job or off-the-job: On-the-job training takes place in a normal working situation, using the actual tools, equipment, documents or materials that trainees will use when fully trained. On-the-job training has a general reputation as most effective for vocational work. Off-the-job training takes place away from normal work situations — implying that the employee does not count as a directly productive worker while such training takes place. Off-the-job training has the advantage that it allows people to get away from work and concentrate more thoroughly on the training itself. This type of training has proven more effective[citation needed] in inculcating concepts and ideas. Training differs from exercise in that people may dabble in exercise as an occasional activity for fun. Training has specific goals of improving one's capability, capacity, and performance. Compare: Education Learning