The Pontifical Mission Societies (PMS) are a worldwide network at the service of the Holy Father to sustain the mission and the young Churches through prayer and charity.
"The four Societies - Propagation of the Faith, St. Peter the Apostle, Holy Childhood and the Missionary Union - have the common purpose of fostering a universal missionary spirit among the People of God... They bring to the Catholic world that spirit of universality and of service to the Church's mission, without which authentic cooperation does not exist." Pope St. John Paul II, Redemptoris Missio, 84
The Society for the Propagation of the Faith, the Missionary Childhood Association, and the Society of St. Peter the Apostle each have a solidarity fund. The graphic featured below explains how the universal solidarity funds work (from the international site). If you would like to see a summary of the results from the 2018-2019 year, click here. You can also access the full report here.