You will need this licence if you intend to operate as an engineer in the certification of the airworthiness of an aircraft.
You may operate under four different categories of maintenance licence: A, B1, B2, and C. Each category of licence has its own privileges, limitations, exclusions and conditions related to the maintenance work that a licensee is authorised to do.
Licence holders are approved to certify that any maintenance undertaken, within their field of expertise, is compliant with the prescribed standards.