Pope John Paul II declared the Sunday after Easter be called “Divine Mercy Sunday.” St. Faustina Kowalska was a Polish nun who received visions from Jesus, including one of Jesus wearing a white garment with beams of red and white coming from His heart, which came to be known as the image of Divine Mercy.
Chaplets are "personal devotionals." They have no set form and vary considerably. In the Roman Catholic Church, while the usual five-decade Dominican rosary is a chaplet, often chaplets have fewer beads than a traditional rosary and a different set of prayers. It is prayed to obtain Christ’s mercy and to bring mercy to others. The chaplet is usually prayed using rosary beads (and in fact the “Hail Mary” is one of the prayers of the chaplet), but its focus is on Christ and the promise of his mercy.
It shows us that through this prayer, we can obtain mercy for ourselves, our family and friends, our communities, our country and even the whole world.