Rule 14.4 Frequency of general meetings sets out how many general meetings must be held in your co-op each year. Generally co-op Rules require the Annual General Meeting (AGM) and the Semi-Annual General Meeting (SAGM).
Other than the required meetings, the Directors may call a special general meeting when they think fit. For example if your Rules require two general meetings per year and your board called a third meeting, that meeting would be a special general meeting.
Some examples of why a co-op board might call a special general meeting include:
Members can also require the board to call a special general meeting through a meeting requisition if enough members make the request in writing – see Rule 14.5 and the specific requirements set out in the Cooperative Association Act. Members may requisition meetings to receive board clarification on co-op issues or to remove a director(s) (when the board has already refused to call a meeting at their request).
You can download a PDF file of this Special General Meeting overview here.