“All persons who have completed their fourteenth year are bound by the law of
abstinence; all adults are bound by the law of fast up to the beginning of their sixtieth year.”  (See the Code of Canon Law, 1252.)

The law of abstinence forbids the eating of meat. The law of fasting allows only one full meal and two lighter meals in the course of the day and prohibits eating between meals. (CCC 1438, 2043)

In the United States, Ash Wednesday and Good Friday are days of fast and abstinence, all other Fridays of Lent are days of abstinence only.

Some form of penance is especially encouraged on all Fridays throughout the year.
Pregnant women and people who are sick are not obliged to fast.

Others who feel they are unable to observe the laws of fast and abstinence should consult a parish priest or confessor.

Fast and abstinence are recognized forms of penance. By doing these and other penance, we can realize the interior change of heart that is so necessary for all Christians.
(CCC1434-1437)

Taken from the “Beliefs and Practices” section of the Archdiocese of Chicago’s web site