Organisations with a large board of directors (such as international labor unions, large corporations with thousands of stock holders or national and international organizations) may have a smaller body of the board, called an executive committee (abbreviated to exco), handle its business. The executive committee may function more like a board than an actual committee.
In any case, an executive committee can only be established through a specific provision in the charter or bylaws of the entity (i.e. a board cannot appoint an executive committee without authorisation to do so). Members of the executive committee may be elected by the overall franchised membership or by the board, depending on the rules of the organisation.
However formed, an executive committee only has such powers and authority that the governing documents of the organisation give it. In some cases, it may be empowered to act on behalf of the board or organisation, while in others, it may only be able to make recommendations.