Trainers work in many different areas, mainly educating employees of companies on specific topics of workplace importance. Some trainers are in-house, and others work for training companies.
Trainers often work within the Human Resources department of a company, fulfilling the most frequent internal needs for education of the workers and management in a company.
In certain cases companies hire external trainers, especially if the needed knowledge is not available within the own trainers pool or if the company is too small to have internal trainers or if the project is too large for the in-house training staff.
Many times people confuse the term training facilitator and trainer. As opposed to the facilitator the trainer does take an active role and transmits mainly knowledge.