Lenten Rules for Catholics

The Season of Lent in the Catholic church begins on Ash Wednesday and concludes on Holy Saturday (the Saturday prior to Easter). This is a 40-day period as the Sundays are not considered part of the season. During Lent, Catholics are called upon to prepare for the Easter celebration through prayer, alms giving, self-denial and penitence.

History

Easter is the most holy of Christian holidays.. The death and resurrection of Jesus Christ is the basis of Christian faith. Lent is a time of grief that ends in celebration. Therefore, Christians typically practice self-denial and increased charity during this time as an homage to Christ's own suffering.

Alms Giving

Alms giving is a staple of most religions. Those who are able are expected to give a portion of their goods to help the less fortunate. today, this typically is a monetary donation to the church. Often, during the Lenten Season, additional fund-raising and charity benefits take place as Catholics focus on the sacrifice that Jesus made for them through his death.

Penitence

Again, this is not a practice that is specific to Lent, but that tends to be practiced with additional fortitude during the season. Catholics are expected to confess their sins and to atone for them in various ways.
While not condone by the Church, self-abuse is not unheard of among zealots. Often this abuse will take aim to recreate some of Christ's own suffering.

Fasting

During the Lenten season, certain fasting rules are to be upheld. While the Canon of the Church calls for fasting on all Fridays, other charitable actions are allowed to be substituted. During Lent, abstinence from eating meat on Fridays is to be observed. Freshwater fish is allowed. Fasting and abstinence is also to be observed on Ash Wednesday.

Self-Denial

Catholics are encouraged to perform additional forms of abstinence during Lent. This is why you will often hear about someone "giving up" something for Lent. Some traditional items may include children abstaining from candy during the Lenten season, adults may extrapolate the fasting requirement so that the abstain from meat throughout the season.
Often, people will utilize this period to give up unhealthy habits such as smoking. This does not strictly follow the intent of the canon as the abstinence is supposed to be for religious reasons rather than health or other such causes.