An executive director works for the company (usually full time) and has a senior role responsible for the strategic and tactical management of the division they run. Typically, they are C-suite roles, such as Chief Executives, Chief Financial Officers, Chief Technology Officers, and other executive division heads.
A non-executive director works in an advisory role as a consultant. The workload can vary, but typically it might be 10 to 40 days a year, including board meetings.