Short answers, pulled from the story.
Pity is a colour print on paper, finished in ink and watercolour, made by William Blake around 1795. It belongs to a group of works known as the Large Colour Prints and depicts a female cherub swooping down to snatch a baby from a prostrate woman below.
Blake's Pity illustrates lines 21-23 of Act 1, Scene 7 of Macbeth, in which the king imagines pity like a naked new-born babe striding the blast, or heaven's cherubim horsed upon the sightless couriers of the air. It is unusual as a literal illustration of a double simile rather than a dramatic scene.
Four impressions survive. The most elaborate is at the Tate Gallery in London (Butlin 310), donated by W. Graham Robertson in 1939. A second is at the Metropolitan Museum of Art, donated by Mrs. Robert W. Goelet in 1958. A third is at the Yale Center for British Art. The fourth, a smaller trial print from a different matrix (Butlin 313), is in the British Museum.
Blake used a monotype method, painting onto gessoed millboard and pressing paper against it to lift an impression, then finishing each print by hand in ink and watercolour. This technique allowed him to pull up to three impressions from a single painted matrix.
In Blake's mythology, pity is a morally ambiguous emotion linked to the failure of inspiration and a further dividing. It is associated with Tharmas, a figure whose frustrated desire turns him into a terror to all living things, and appears in the confrontation between a feminine Pity and a masculine fiery force in the figure of Urizen.
Both prints date to around 1795 and both reference Macbeth. Scholars read them as opposing images: The Night of Enitharmon's Joy depicts a Hecate surrounded by nightmare creatures, while Pity is seen as offering a possibility of salvation in the fallen world through the emotion it portrays.