Answer:
Craft Union membership is for those that are engaged or possess a particular skill.
Industry Unions as inferred, is for people in the same industry regardless of the jobs and skills they possess in that industry.
Local Unions are for those working under a shared employer in an industry.
Union Stewards work in a company but also in a Union to push the agendas of employees.
Craft Union.
Industry Union
Local Unions
Union Stewards.