Qualifications/licences are specific to either "base maintenance" (hangar/overhaul work) or "line maintenance" experience (day-to-day maintenance on the line);

licences further specify whether or not they confer "certifying" authority (authority to sign for completion, or certification, of a job);

maintenance licences are task-related in the lowest category, or type-rated in the higher categories. They also state specialisation (mechanical, avionics, rotary-wing, etc);

finally, the combination of an individual's academic qualifications, training, experience and years of service are reflected in the licence "category", with Category A indicating low experience/ qualifications and C indicating the highest level.

Source: Flight International