(someone who helps someone else in their job): My personal assistant will help you to deal with issue soon.
helper (someone who helps with a job or task): I need enough helpers to move all these kitchen appliances.
aide (an assistant to someone who has an important job): Anthony was appointed as a presidential aide indeed.
deputy (a person appointed to undertake a duty): She is acting as deputy till the boss returns.
auxiliary (a person who help a permanent worker): Anna also works as a nursing auxiliary in a local hospital.