"The Pre-Raphaelite Brotherhood was started in 1848 by Dante Gabriel Rossetti, John Everett Millais and William Holman Hunt, as a reaction against what they saw as the stale, formula-driven art produced by the Royal Academy at the time. They aimed to go back to a more genuine art, exemplified as they saw it by the work of the Nazarenes, and rooted in realism and truth to nature."
Pre-Raphaelite painting is bright and extremely real, though it is not the obsessive, hyper-real optical illusion of Vermeer. It is natural in its contrivances. As a whole, the body of work is focused on the characters of poetry and religion, from Shakespeare to Coleridge to Greek mythology and biblical imagery. When I look at it and try to think of a simple word or two to describe it, I think "lush." Pre-raphaelite painting is meant to be arresting, to seem realistic, yet idealized and sentimental - this can give it a sexual dimension I haven't seen in anything that came before it. This should not imply that the Pre-raphaelites were either single minded, or sexually or dramatically preoccupied. Just that those paintings often get the most attention.
This famous quote attributed to John Ruskin is ubiquitously given when describing the movement:
"We begin by telling the youth of fifteen or sixteen that Nature is full of faults, and that he is to improve her; but that Raphael is perfection, and that the more he copies Raphael the better; that after much copying of Raphael, he is to try what he can do himself in a Raphaelesque, but yet original manner: that is to say, he is to try to do something very clever, all out of his own head, but yet this clever something is to be properly subjected to Raphaelesque rules, is to have a principal light occupying one seventh of its space, and a principal shadow occupying one third of the same; that no two people's heads in the picture are to be turned the same way, and that all the personages represented are to have ideal beauty of the highest order..."
Many of the brotherhood's most popular works today were not produced by its founders, but by the generation of artists they inspired, including William Morris, Frank Dicksee, Evelyn De Morgan, Edmund Blair Leighton, Sir Edward Burne-Jones, Frederick Sandys, and, my personal favorite, John Waterhouse.