The Jubilee is a special year of grace that has its origins in the Jewish tradition.
In the Catholic Church, it is a year of the remission of sins, conversion, and sacramental penance. It’s a year of pilgrimages, of a focus on the spiritual life, of confession and special Masses, and of a general turn towards God in thanksgiving, and in repentance.
Initially scheduled every 50 years, nowadays it occurs every 25 years. The Jubilee (or Holy Year) is called Ordinary (or Major) when tied to predetermined deadlines and Extraordinary (or Minor) when proclaimed for some particularly significant event.