Both types of training locations conduct and deliver NCCER training under an Accredited Training Sponsor (ATS). The differences include:
Training Unit (TU) — Non-school locations, such as a job site, company or customer office. More short-term.
Accredited Training & Education Facility (ATEF) — School locations, high school, technical school, community college or education facilities.
Check here for step-by-step instructions to register a training location.