The first and most important is the Camerlengo, currently held by Italian Cardinal Tarcisio Bertone. He will temporarily take over control of the Vatican's every day affairs. However, for more important matters, usually brought to the Pope, they must be presented to the College of Cardinals during general congregations, which take place every day leading up to the conclave.
JUAN IGNACIO ARRIETA
Secretary, Pontifical Council for Legislative Texts
February 16, 2004
"Afterward, between them, there are three cardinals, in addition to and led by the Camerlengo, that form a particular congregation. They execute the decisions taken by the general congregation formed by all the cardinals.”
The second position is the Major Penitentiary, held by Portuguese Cardinal Manuel Monteiro de Castro. His task includes the absolution of major sins, such as a priest who breaks their seal of confession, or granting indulgences.
The third position is the Vicar General of Rome, Cardinal Agostino Vallini. As the Pope usually tends to the entire Catholic Church, he appoints a Vicar General to take care of the faithful in Rome. The pastoral work continues even when there is no Bishop of Rome (Pope).
During the papal vacancy, no laws can be created or changed. Any matters that can be held off will be done so, until the new Pope takes the helm of the Catholic Church.