there is a sticky for all past questions about Lent including this one, which is also discussed in several open threads. I suggest a search and careful reading because some of them contain very helpful refelections on the purpose and spiritual dimension of fasting and abstinence. Catholics must abstain from eating meat, that is the flesh of warm blooded animals, or whatever is defined as meat by the bishop in their locality on the days appointed, and must fast on Ash Wednesday and Good Friday. Currently in the US days of abstinence are Fridays in Lent and Ash Wednesday. In the Latin Rite dairy, fats and condiments made from animal products and fish are allowed on days of abstinence. There is an ongoing discussion on the Eastern Catholicism forum on their rules which are stricter.
