Animation is a filmmaking technique whereby pictures are created or manipulated and then played in sequence to create the illusion of moving images. In traditional animation, images are drawn or painted by hand on transparent celluloid sheets to be photographed and exhibited on film. Animation has been recognized as an artistic medium, specifically within the entertainment industry. Many animations are either traditional animations or computer animations made with computer-generated imagery (CGI). Stop motion animation, in particular claymation, is also prominent alongside these other forms, albeit to a lesser degree.

Animation is contrasted with live action, although the two do not exist in isolation. Many filmmakers have produced films that are a hybrid of the two. As CGI increasingly approximates photographic imagery, filmmakers can relatively easily composite 3D animated visual effects (VFX) into their film, rather than using practical effects.

Computer animation can be very detailed 3D animation, while 2D computer animation (which may have the look of traditional animation) can be used for stylistic reasons, low bandwidth, or faster real-time renderings. Other common animation methods apply a stop motion technique to two- and three-dimensional objects like paper cutouts, puppets, or clay figures.

An animated cartoon, or simply a cartoon, is an animated film, usually short, that features an exaggerated style. This style is often inspired by comic strips, gag cartoons, and other non-animated art forms. Cartoons frequently include anthropomorphic animals, superheroes, or the adventures of human protagonists. The action often revolves around exaggerated physical humor, particularly in predator/prey dynamics (e.g. cats and mice, coyotes and birds), where violent pratfalls such as falls, collisions, and explosions occur, often in ways that would be lethal in the real life.

During the late 1980s, the term "cartoon" was shortened to toon, referring to characters in animated productions, or more specifically, cartoonishly-drawn characters. This term gained popularity first in 1988 with the live-action/animated hybrid film Who Framed Roger Rabbit, which introduced ToonTown, a world inhabited by various animated cartoon characters. In 1990, Tiny Toon Adventures embraced the classic cartoon spirit, introducing a new generation of cartoon characters. Then, in 1993, Animaniacs followed, featuring the three rubber-hose-styled Warner siblings, Yakko Warner, Wakko Warner, and Dot Warner, who are trapped in the 1930s, eventually escaped and found themselves in the Warner Bros. water tower in the 1990s.

The illusion of animation—as in motion pictures in general—has traditionally been attributed to the persistence of vision and later to the phi phenomenon and beta movement, but the exact neurological causes are still uncertain. The illusion of motion caused by a rapid succession of images that minimally differ from each other, with unnoticeable interruptions, is a stroboscopic effect. While animators traditionally used to draw each part of the movements and changes of figures on transparent cels that could be moved over a separate background, computer animation is usually based on programming paths between key frames to maneuver digitally created figures throughout a digitally created environment.

Analog mechanical animation media that rely on the rapid display of sequential images include the phenakistiscope, zoetrope, flip book, praxinoscope, and film. Television and video are popular electronic animation media that originally were analog and now operate digitally. For display on computers, technology such as the animated GIF and Flash animation were developed.

In addition to short films, feature films, television series, animated GIFs, and other media dedicated to the display of moving images, animation is also prevalent in video games, motion graphics, user interfaces, and visual effects.