At an early stage in the life of the church, the influence of the Greek brought (with its tendency to view sin as a necessary flaw in human nature) made it necessary for the church to determine the relative seriousnes of various moral faults. This ultimately gave rise to what is commonly referred to as the seven deadly sins--a concept that occupies an important place in the order and dicipline of the Roman Catholic church.
These sins are pride, covetousness, lust, envy, gluttony, anger, and sloth.
K.E. Kirk stresses that they are to be understood as "capital" or "root" sins rather than "deadly" or "mortal" (viz. sins which cut one off from his true last end). They are the "sinful propensities which reveal themselves in particular sinful acts." The list represents an attempt to enumerate the primary instincts that are most likely to give rise to sin.
Even though the original classification may have been more monastic in orgin, under the influence of gregory the great, the scope was widened, and along with the seven cardinal virtues they came to constitute the moral standards and tests of the early catholic church. In medieval scholasticism they were the subject of considerable attention.
Hope that was helpful and interesting. ^^