The discipline of fasting allows only one full meal a day, but does not prohibit taking some food in the morning and evening (the order of meals is optional.) The law of fasting also requires no eating of food between meals. The quantity of food taken at the two lesser meals should not exceed the quantity at the full meal. Drinking ordinary liquids does not break the fast. Fasting is to be observed by all Catholics from the completion of their 18th year to the beginning of their 60th year. 
The discipline of abstinence forbids the eating of meat, but not of eggs, the products of milk or condiments made of animal fat. Permissible are soups, gravy and sauces flavored with meat. Abstinence is to be observed by all Catholics from the completion of their 14th year - from the day after their 14th birthday - and throughout life. 
Days of fasting and abstinence are binding only to those in good health. For more information about these disciplines, contact the Archdiocesan Office for Christian Worship at 313-237-5934 or aod.org. 

During Lent
During the Season of Lent, Catholics are obligated to practice the disciplines of fasting and abstinence. We practice these Lenten disciplines as a means of doing penance. Ash Wednesday is a day of fast and abstinence. The Fridays of Lent are day of abstinence. 

Good Friday and Holy Saturday
Since Lent ends on Holy Thursday evening, the obligatory fast and abstinence we keep on Good Friday and the optional abstinence we can keep on Holy Saturday are not means of doing penance. These disciplines are meant to be a fast/abstinence in anticipation of Easter. 
Good Friday is a day of fast and abstinence. On Holy Saturday, it is recommended we maintain abstinence (and, if possible, fasting) until the evening celebration of the Easter Vigil Mass.