I seldom heard the apprentice these years, from my understanding there are 2 difference: 1 Trainee employee is actual employee and hired by certain organizations, organizations have to pay them salary and provide certain benefits, apprentice is not employee, but he/she may get some subsidy from the organizations or individuals. 2, both trainee employee and apprentice are under agreement with organizations/individuals, but agreement between trainee employee and organziations should be standard labor contract, agreement between apprentice and organizations/individuals should be loose statement regarding learning environment, subsidy/benefits and contract period.