Berachos, chapter 6. The Mishnah teaches that one who recites the berachah on wine before the berachah of "Hamotzi" includes in that berachah - and thereby exempts - even the wine that comes after the meal, at its conclusion and before Birkas Hamazon.
When does this apply?
The rule that the berachah on wine at the start of the meal covers the wine that comes after it, before Birkas Hamazon, applies - as the Gemara explains - only on Shabbos and Yom Tov. The reason is 'kevi'us se'udah al yayin', that the meal is established upon wine: on Shabbos and Yom Tov wine is treated as significant, and a person has in mind to drink wine even after the meal, and therefore the berachah on the wine before the meal exempts the wine that follows it. During the rest of the year, however, a new berachah is required on the wine after the meal, since we assume that he did not have additional wine in mind. Only on Shabbos and Yom Tov, where the assumption is the opposite, is the later wine included in the first berachah.
Parperes - two explanations:
First explanation: 'Parperes' is anything eaten as an accompaniment to bread - fish, meat, vegetables and other items eaten as part of the meal. According to this, the Mishnah is saying: one who recites a berachah on the parperes, such as a small portion served before the meal itself actually begins (in Yiddish: forshpeis), a bit of fish or a bit of meat - his berachah covers even the parperes brought after the meal is over, before Birkas Hamazon is recited.
Second explanation: 'Parperaos' are a type of bread product whose berachah is 'Mezonos', such as biscuits or pretzels. These too are included in the rule: one who recites the berachah on them before the meal, his berachah is effective also when he eats them after the meal, in place of dessert.
The relationship between the berachos on bread and on parperaos:
One who recites the berachah on bread - his berachah removes any need for a berachah on the parperaos, both according to the explanation that parperaos are the items that accompany bread, and according to the explanation that they are a type of bread whose berachah is 'Mezonos'.
One who recites the berachah on the parperaos - whether the berachah on fish and meat, or the berachah of 'Mezonos' on the biscuit or pretzel - his berachah does not exempt the bread. A berachah of 'Mezonos' or of 'Shehakol' has no power to cover bread.
The opinion of Beis Shammai:
Beis Shammai add: "Af lo ma'aseh kederah" - not even a dish cooked in a pot. 'Ma'aseh kederah' refers to items such as porridge, oatmeal or pasta - foods that have neither the form of bread nor the texture of bread, and are not in the category of 'pas haba'ah b'kisnin'. These foods are not included in the berachah he recited on the parperes, whether 'parperes' here means the fish and meat, or whether it means a biscuit or a 'Mezonos' item of the pretzel type.
In summary: we learned that the berachah on wine before the meal exempts the wine that follows it, and this applies only on Shabbos and Yom Tov because of 'kevi'us se'udah al yayin'; that the berachah on the parperes before the meal exempts the parperes that follows it, both according to the explanation that parperaos are the accompaniments to bread and according to the explanation that they are a type of bread whose berachah is 'Mezonos'; that the berachah on bread exempts the parperaos, while the parperaos do not exempt the bread; and that according to Beis Shammai even 'ma'aseh kederah' is not included in the berachah on the parperes.