The Anglican church does not end with the parish or the diocese, or the synod of the diocese. The Anglican Church covers the whole of Canada, from shore to shore to shore, and through the Anglican Communion extends around the world on all the inhabited continents.
General Synod of the Anglican Church of Canada
The key thing to understanding the national church is to appreciate that it is a federation. The 31 dioceses which make up the Anglican Church of Canada have delegated power to the national church, the central structure of which is General Synod.
Each diocesan synod elects and sends a number of lay and clerical delegates. All diocesan bishops are also members of General Synod. It meets once every three years.
The dioceses have delegated substantial powers to the General Synod, including those governing doctrine, worship, and discipline to the national church. So, matters around forms of worship, the licensing and dismissal of clergy, and the Christian teaching about marriage all fall under the power of General Synod. General Synod operates through committees and General Synod staff.
Council of General Synod
Just as we have a Diocesan Council, and a parish vestry has a Parish Council, so there is a Council of General Synod (COGS). It meets twice a year between sessions of General Synod.