The Catechism of the Catholic Church has this to say about the Fruits of the Holy Spirit:

"The fruits of the Spirit are perfections that the Holy Spirit forms in us as the first fruits of eternal glory. The tradition of the Church lists twelve of them: ‘charity, joy, peace, patience, kindness, goodness, generosity, gentleness, faithfulness, modesty, self-control, chastity.’"

These fruits are the result of growth in the gifts of the Holy Spirit. These fruits are tendencies rather than mere willingness, because "the spirit is willing but the flesh is weak." In the person who possesses a Fruit of the Spirit, this willingness bears fruit in the life and behavior of the person.

Charity
Charity is love, both of God and of neighbor. It is our love for God above all things for his own sake and our neighbor as ourselves for the love of God.

In addition, Paul explained in the 13th chapter of 1 Corinthians that Charity IS the greatest…far above any of the other Fruits. Charity is about giving of oneself. When Jesus died on the cross, it wasn’t about anything other than Charity.

1 Cor 13:4-7 4 Charity suffereth long, and is kind; charity envieth not; charity vaunteth not itself, is not puffed up, 5 Doth not behave itself unseemly, seeketh not her own, is not easily provoked, thinketh no evil; 6 Rejoiceth not in iniquity, but rejoiceth in the truth; 7 Beareth all things, believeth all things, hopeth all things, endureth all things. 13 And now abideth faith, hope, charity, these three; but the greatest of these is charity. (KJV)’

Joy

Joy is the happiness found in union with the Lord. As C.S. Lewis described it, it is a glimpse of the perfect happiness of heaven that leads us to desire heaven.

Peace

Peace refers to dealing justly with the world, as well as remaining in good conscience before God.

Patience

Patience, also known as long-suffering, refers to the tendency to endure both temptation and suffering without it leading to sin.

Kindness

Kindness, also known as Benignity, is the tendency toward acting kindly and doing good.

Goodness

Goodness is the tendency to avoid sin and do good.

Generosity

Generosity is an openness to sharing one’s own gifts and goods with others. It is the opposite of both gluttony and envy.

Gentleness

Gentleness, also known as mildness, is the tendency to allow provocations to go unanswered.

Faithfulness

Faithfulness is the standing strong in faith, and strength against diversion away from faith and virtue.

Contrasted with the Gifts of the Holy Spirit
There is also a catalogue of the Seven gifts of the Holy Spirit based on Isaiah 11:2. They are wisdom, understanding, counsel, fortitude, knowledge, piety and fear of God. The principal distinction between these two lists would seem to be that the seven gifts of the Holy Spirit are what Christians are to pray for, and the fruits of the Holy Spirit are the manifestation of those gifts.

See also

Holy Spirit

Spiritual gift

References
Note: Based on Galatians 5:22-23, there is one fruit of the Spirit in nine parts: "But the fruit of the Spirit is love, joy, peace, patience, kindness, goodness, faithfulness, gentleness, self-control; against such things there is no law."