Animation is a medium that takes a series of pictures with very slight difference from one to another, and plays them in rapid succession, giving you the illusion of a moving picture. This is what Television and Film do too, but when we talk about them here at All The Tropes, we generally mean works that are mostly created images rather than captured images. Even this definition becomes fuzzy, with CGI scenes and Post Processing Video Effects, but it mostly falls into categories including hand-drawn cels, computer-drawn stories (mostly non-interactive, otherwise they'd be computer games), Stop Motion with clay or such, Pixilation with live actors, or some mixture thereof.
One of the things that determines whether something is animation is the usage of Animation Tropes. Animation is frequently accompanied by Voice Actors adding sound to the characters — though they too may one day lose their jobs to robots through the likes of Vocaloids.
We have a section on the History of Animation.
On this site we tend to group animation by its region of origin. Japanese animation is called Anime, along with that from other Western Pacific Rim cultures. We have Eastern Animation from the old Soviet Bloc. And Western Animation represents much of the rest of the world, including Europe, Australia, and the Americas.