Computer animation — also known as digital animation — is a form of computer generated imagery (CGI) that focuses on moving images. While CGI can refer to static digitally generated images, computer animation is only about moving ones. Films like Toy Story and Frozen are two popular examples.
At their core, computer animations essentially bring to life static images or objects by digitally introducing movement to them. Animators use software to draw, model and move them in their desired way. The static image displays on a computer and constantly replaces it with an almost identical one to create the movement (known as keyframing).
You can use a variety of computer animation algorithms and techniques to create digital animation. The exact methods differ depending on the specific task at hand — from keyframing to motion capture and more.