The tradition of holding Synods at times when the Church faces particular challenges or decisions stretches back to the earliest days of the Church and the Synod of Jerusalem (c. 50AD) that is recounted in the Acts of the Apostles (chapter 15). This Synod dealt with the question of whether Gentiles who converted to Christianity should be required to follow the rules of Judaism that are laid out in the Torah.
Closer to home we are familiar with the Synod of Whitby (664AD) which ruled that the date of Easter should be set in line with Rome rather than using the local Celtic custom.
Synods, which had been somewhat out of fashion for a period, made a comeback after the Second Vatican Council when Pope Paul VI established the Synod of Bishops as an advisory body for the Pope.
More recently under Pope Francis Synods have come to the fore and he has described the path of synodality as the path that Christ desires for His Church in the third millennium.
During his time as Bishop of Rome, Pope Francis has convened Synods on the Family (2015)and on Youth (2018). Inspired by his example several dioceses around the world have held local Synods including Limerick (2016), Detroit (2016), Wellington (2017), and now Liverpool in 2020/2021.