“Mardi Gras” /ˈmɑrdiɡrɑː/, “Mardi Gras season,” “‘Fat Tuesday'” and “Carnival season,” in English, refer to events of the Carnival celebrations, beginning on or after the Epiphany or Kings day and culminating on the day before Ash Wednesday. Mardi Gras is French for Fat Tuesday, referring to the practice of the last night of eating richer, fatty foods before the ritual fasting of the Lenten season, which begins on Ash Wednesday. The day is sometimes referred to as Shrove Tuesday, from the word shrive, meaning “confess.” Related popular practices are associated with celebrations before the fasting and religious obligations associated with the penitential season of Lent.

Source: Wikipedia.com