Did you bother to read?  I thought not...from the very article:
 
To facilitate explanation, it may be well to state what an indulgence is not. It is not a permission to commit 
sin, nor a pardon of future 
sin; neither could be granted by any power. It is not the forgiveness of the guilt of 
sin; it supposes that the 
sin has already been forgiven. It is not an 
exemption from any 
law or 
duty, and much less from the 
obligation consequent on certain kinds of 
sin, e.g., 
restitution; on the contrary, it means a more complete payment of the 
debt which the sinner owes to 
God. It does not confer immunity from 
temptation or remove the possibility of subsequent lapses into 
sin. Least of all is an 
indulgence the purchase of a pardon which secures the buyer's 
salvation or releases the 
soul of another from 
Purgatory. The absurdity of such notions must be obvious to any one who forms a correct 
idea of what the 
Catholic Church really teaches on this subject.
 
An 
indulgence is the extra-sacramental remission of the temporal punishment due, in 
God's justice, to 
sin that has been forgiven, which remission is granted by the 
Church in the exercise of the 
power of the keys, through the application of the superabundant 
merits of Christ and of the 
saints, and for some just and reasonable motive. Regarding this definition, the following points are to be noted: 
- In the Sacrament of Baptism not only is the guilt of sin remitted, but also all the penalties attached to sin. In the Sacrament of Penance the guilt of sin is removed, and with it the eternal punishment due to mortal sin; but there still remains the temporal punishment required by Divine justice, and this requirement must be fulfilled either in the present life or in the world to come, i.e., in Purgatory. An indulgence offers the penitent sinner the means of discharging this debt during his life on earth.
 
- Some writs of indulgencenone of them, however, issued by any pope or council (Pesch, Tr. Dogm., VII, 196, no. 464)contain the expression, "indulgentia a culpa et a poena", i.e. release from guilt and from punishment; and this has occasioned considerable misunderstanding (cf. Lea, "History" etc. III, 54 sqq.). The real meaning of the formula is that, indulgences presupposing the Sacrament of Penance, the penitent, after receiving sacramental absolution from the guilt of sin, is afterwards freed from the temporal penalty by the indulgence (Bellarmine, "De Indulg"., I, 7). In other words, sin is fully pardoned, i.e. its effects entirely obliterated, only when complete reparation, and consequently release from penalty as well as from guilt, has been made. Hence Clement V (1305-1314) condemned the practice of those purveyors of indulgences who pretended to absolve "a culpa et a poena" (Clement, I. v, tit. 9, c. ii); the Council of Constance (1418) revoked (Sess. XLII, n. 14) all indulgences containing the said formula; Benedict XIV (1740-1758) treats them as spurious indulgences granted in this form, which he ascribes to the illicit practices of the "quaestores" or purveyors (De Syn. dioeces., VIII, viii. 7).
 
- The satisfaction, usually called the "penance", imposed by the confessor when he gives absolution is an integral part of the Sacrament of Penance; an indulgence is extra-sacramental; it presupposes the effects obtained by confession, contrition, and sacramental satisfaction. It differs also from the penitential works undertaken of his own accord by the repentant sinner  prayer, fasting, alms-giving  in that these are personal and get their value from the merit of him who performs them, whereas an indulgence places at the penitent's disposal the merits of Christ and of the saints, which form the "Treasury" of the Church.
 
- An indulgence is valid both in the tribunal of the Church and in the tribunal of God. This means that it not only releases the penitent from his indebtedness to the Church or from the obligation of performing canonical penance, but also from the temporal punishment which he has incurred in the sight of God and which, without the indulgence, he would have to undergo in order to satisfy Divine justice. This, however, does not imply that the Church pretends to set aside the claim of God's justice or that she allows the sinner to repudiate his debt. As St. Thomas says (Supplement.25.1 ad 2um), "He who gains indulgences is not thereby released outright from what he owes as penalty, but is provided with the means of paying it." The Church therefore neither leaves the penitent helplessly in debt nor acquits him of all further accounting; she enables him to meet his obligations.
 
- In granting an indulgence, the grantor (pope or bishop) does not offer his personal merits in lieu of what God demands from the sinner. He acts in his official capacity as having jurisdiction in the Church, from whose spiritual treasury he draws the means wherewith payment is to be made. The Church herself is not the absolute owner, but simply the administratrix, of the superabundant merits which that treasury contains. In applying them, she keeps in view both the design of God's mercy and the demands of God's justice. She therefore determines the amount of each concession, as well as the conditions which the penitent must fulfill if he would gain the indulgence.