Short answers, pulled from the story.
Post-Impressionism was a predominantly French art movement that developed roughly between 1886 and 1905, from the last Impressionist exhibition to the birth of Fauvism. It emerged as a reaction against the Impressionists' concern for the naturalistic depiction of light and color, emphasizing instead abstract qualities, geometric forms, and symbolic content.
The principal Post-Impressionist artists were Paul Cezanne, Paul Gauguin, Vincent van Gogh, and Georges Seurat. Cezanne is known as the father of Post-Impressionism.
The art critic Roger Fry first used the term Post-Impressionism in 1906, and again in 1910 for his exhibition Manet and the Post-Impressionists at the Grafton Galleries in London. Critic Frank Rutter had put the term in print three weeks earlier, in Art News of the 15th of October 1910, describing Othon Friesz as a post-impressionist leader.
Post-Impressionism encompasses Les Nabis, Neo-Impressionism, Symbolism, Cloisonnism, the Pont-Aven School, and Synthetism, along with some later Impressionists' work. Cloisonnism was introduced in 1888 and Synthetism was coined in 1889.
Post-Impressionists extended Impressionism by continuing to use vivid colors, impasto, and painting from life, but rejected its limitations. They were more inclined to emphasize geometric forms, distort form for expressive effect, and use unnatural or modified color, putting harmony and structural arrangement ahead of naturalism.
Canadian Post-Impressionism was an offshoot of the movement. In 1913 the Art Association of Montreal's Spring show included work by Randolph Hewton, A. Y. Jackson, and John Lyman, and Canadian artists associated with the name include James Wilson Morrice, David Milne, Tom Thomson, members of the Group of Seven, and Emily Carr.