This famous painting is called "Seven Acts of Mercy" by Caravaggio - Here's the interpretation - 

Bury the dead - In the background, two men carry a dead man (of whom only the feet are visible)

Visit the imprisoned, and feed the hungry - 
On the right, a woman visits an imprisoned man and gives him milk from her breast. That image alludes to the classic story of "Roman Charity." 

Shelter the homeless - A pilgrim (third from left, identified by the shell in his hat) asks an innkeeper (at far left) for shelter. 

Clothe the naked - St. Martin, fourth from the left, has torn his robe in half and given it to the naked beggar in the foreground, recalling the saint's popular legend. 

Visit the sick - St. Martin greets and comforts the beggar who is cripple. 

Refresh the thirsty - Samson drinks water from the jawbone of an ass. (top left)

The angel at the center of Caravaggio's piece transmits the grace that inspires humanity to be merciful.