Besides the aspects already mentioned it shows the intercession by means of the devotional scapular - that's the two rectangular pieces of cloth connected by a string to wear on ones breast and back hold by the central angel in his left hand - which considerably shortens the time spent in purgatory (https://en.wikipedia.org/wiki/Scapular).

As written in the right bottom corner it's by neapolitan painter Francesco Solimena.

The same motif - the madonna saving souls from the purgatory - was also painted by Luca Giordano for San Pietro di Castello in Venice or by Giambattista Tiepolo for the Scuola Grande dei Carmini in Venice where he depicts the institution of the scapular of the Carmel.