Key Points Regarding Sundays in Lent:
The official days of fast and abstinence are Ash Wednesday and Good Friday, and all Fridays of Lent, not Sundays. Because Sunday is a celebration of the Resurrection, the penance of Lent is paused, allowing for a reprieve from voluntary, self-imposed sacrifices (e.g., giving up sweets).
While Catholics can break their fast on Sundays, they are not required to do so. Many choose to continue their sacrifices throughout the entire period.
Despite the break in fasting, the six Sundays of Lent still belong to the liturgical season of Lent.