Simply put, a synod is a meeting or assembly of church leaders. In the Eastern and Oriental Orthodox Churches synods have been used for centuries to gather bishops and laypeople to reach consensus on important issues.  The Roman Catholic Church has used ecumenical councils.
 

Pope Pius VI instituted a model of synods that met every four years but did not have the power to make binding decisions.

Pope Francis is broadening the vision of synods and has held extraordinary synods, like those on the family, young people, and the Amazon. Before each gathering, Pope Francis urged bishops to hold local listening sessions in their dioceses, and he has invited more laypeople to participate in the bishops' meetings in Rome.

On Oct. 10, 2021, Pope Francis convened the synod officially called "For a Synodal Church: Communion, Participation, and Mission."  

Next week we will look at what the phases are for this synod.