"Cheesefare Week"

This excerpt is taken from:

https://orthodoxwiki.org/Cheesefare_Week

Cheesefare Week is also known as Maslenitsa (Ма́сленица), Butter Week, or Pancake week.  It is celebrated during the last week before Great Lent - that is, the seventh week before Pascha. Cheesefare roughly corresponds to the Western Carnival (Mardi Gras), except that Orthodox Lent begins on a Monday instead of a Wednesday, and the Orthodox date of Easter can differ greatly from the Western date. 

During Cheesefare week, meat is already forbidden to Orthodox Christians, making it a "meat-fast week". During Lent, meat, fish, dairy products and eggs are forbidden. Furthermore, Lent also excludes parties, secular music, dancing and other distractions from the spiritual life. Thus, Cheesefare represents the last chance to partake of dairy products and those social activities that are not appropriate during the more prayerful, sober and introspective Lenten season.

Russian Traditions

The most characteristic element of Cheesefare in Russian tradition is Blini (Russian pancakes/crepes). Round and golden, they are made from the rich foods still allowed by the Orthodox tradition: butter, eggs, and milk.

In some regions, each day of Cheesefare had its traditional activity: one day for sleigh-riding, another for the sons-in-law to visit their parents-in-law, another day for visiting the godparents, etc. 

Sunday of Forgiveness

The last day of Cheesefare Week is called "Forgiveness Sunday", indicating the desire for God's forgiveness that lies at the heart of Great Lent. At Vespers on Sunday evening, all the people ask forgiveness of one another, and thus Great Lent begins. Another name for Forgiveness Sunday is "Cheesefare Sunday," because for Orthodox Christians, it is the last day on which dairy products may be consumed until Pascha. Fish, wine, and olive oil will also be forbidden on most days of Great Lent. The day following Cheesefare Sunday is called Clean Monday, because everyone has confessed their sins, asked forgiveness, and begun Great Lent with a clean slate.