Part-66 is the European regulatory framework used for aircraft maintenance licence categories and associated knowledge/experience requirements. Holding a licence is not the same as holding a company authorization for a particular aircraft type or task.
B1 categories are generally associated with mechanical maintenance areas, while B2 is associated with avionics. For real applications, always check current authority requirements, module status, experience records and approved training conditions.
This page is for career awareness only. Use the current official documents of the relevant authority for licence applications or regulatory interpretation.