Short answers, pulled from the story.
Animation is a filmmaking technique where images are created or manipulated and then played in sequence to create the illusion of moving images. The effect is a stroboscopic one, produced by a rapid succession of images that differ only slightly with unnoticeable interruptions. It has traditionally been credited to persistence of vision and later to the phi phenomenon and beta movement.
The word animation comes from the Latin word animatio, meaning bestowing of life. The earlier meaning of the English word is liveliness, which has been in use far longer than its meaning as a moving-image medium.
In 1832, the Belgian inventor Joseph Plateau built the phenakistoscope, which introduced the principle of persistence of vision behind modern animation. The principle was later applied in William George Horner's zoetrope, the flip book, the praxinoscope, and film.
In 1917, the Italian-Argentine director Quirino Cristiani made El Apostol, the first feature-length animated film, which was a critical and commercial success and is now lost. The oldest extant animated feature is Lotte Reiniger's German silhouette film Die Abenteuer des Prinzen Achmed, released in 1926.
In 1928, Steamboat Willie introduced Mickey Mouse and Minnie Mouse and popularized film with synchronized sound, putting Walt Disney's studio at the forefront of the industry. Although Disney's output has always been small relative to total global animation, the studio has overwhelmingly dominated the aesthetic norms of animation ever since.
The animation market was estimated to be worth about 80 billion US dollars in 2010, rising to an estimated 370 billion US dollars by 2021. Animated feature-length films returned the highest gross margins, around 52 percent, of all film genres between 2004 and 2013.
Most cel animation studios switched to producing mostly computer-animated films around the 1990s because it proved cheaper and more profitable. Pixar's Toy Story in 1995 was the first computer-animated feature in the 3D style, and its success made that technique dominant.