Before and after eating a meal with bread, one is supposed to say a blessing, thanking G-d for the food. The prayer said after, called Birkat HaMazon or Grace After Meals, can be found in a Birkon (Birkonim in plural), which is essentially a small booklet or pamphlet containing just Birkat HaMazon. During special occasions like a Brit Milah (baby boy circumcision and naming ceremony after 8 days of being born) and Sheva Brachot (7 meals after a couple gets married), there are certain additions to the regular Grace After Meals that is said. While it is said everyday, most people make it a priority to say it on Shabbat.