Rococo, often called late Baroque, was an architectural and artistic style developed in France in the first half of the eighteenth century. The king of France, Louis XV is often thought to be a key patron and supporter of the movement-- a very likely hypothesis considering the monarch's need to differentiate himself from the king who proceeded him: Louis XIV (a key patron of the Baroque style).
The Rococo Period is known for its lighter and more airy tone, contrasting the heavy dark tone of the preceding Baroque era. It is characterized by its use of pastels and asymmetry, along with the repetitive use of symbols such as shell motifs, and an idealized version of nature. Rococo styling brought about a new wave of romanticism; the new idea of finding a soulmate, someone whom you love, as opposed to the arranged marriages common in the past.
In many ways Rococo is an extension of the Baroque. Rococo takes all of the tropes and trends of Baroque art and exaggerates them until there is nothing but ornamentation and artifice left.