section staff; member of a section
Refers to a person who belongs to a 課 (section/division) in a company or organization. Neutral, everyday business term.
He is a member of the sales section.
All the section staff attended the meeting.
The section chief informed the staff of the new policy.
All the section staff gathered for the meeting.
社員 simply means a company employee in general, while 課員 narrows this down to someone belonging to a specific 課 (section).
Compound of 課 (section, division) and 員 (member, staff).