This is a book that too can give you a nice overview:
Order the book:
usccbpublishing.org/productdetails.cfm?PC=701
Online:
vatican.va/archive/compendium_ccc/documents/archive_2005_compendium-ccc_en.html
Excerpt:
SIN
- What does the acceptance of God’s mercy require from us?
1846-1848
1870
It requires that we admit our faults and repent of our sins. God himself by his Word and his Spirit lays bare our sins and gives us the truth of conscience and the hope of forgiveness.
- What is sin?
1849-1851
1871-1872
Sin is “a word, an act, or a desire contrary to the eternal Law” (Saint Augustine). It is an offense against God in disobedience to his love. It wounds human nature and injures human solidarity. Christ in his passion fully revealed the seriousness of sin and overcame it with his mercy.
- Is there a variety of sins?
1852-1853
1873
There are a great many kinds of sins. They can be distinguished according to their object or according to the virtues or commandments which they violate. They can directly concern God, neighbor, or ourselves. They can also be divided into sins of thought, of word, of deed, or of omission.
- How are sins distinguished according to their gravity?
1854
A distinction is made between mortal and venial sin.
- When does one commit a mortal sin?
1855-1861
1874
One commits a mortal sin when there are simultaneously present: grave matter, full knowledge, and deliberate consent. This sin destroys charity in us, deprives us of sanctifying grace, and, if unrepented, leads us to the eternal death of hell. It can be forgiven in the ordinary way by means of the sacraments of Baptism and of Penance or Reconciliation.
- When does one commit a venial sin?
1862-1864
1875
One commits a venial sin, which is essentially different from a mortal sin, when the matter involved is less serious or, even if it is grave, when full knowledge or complete consent are absent. Venial sin does not break the covenant with God but it weakens charity and manifests a disordered affection for created goods. It impedes the progress of a soul in the exercise of the virtues and in the practice of moral good. It merits temporal punishment which purifies.