CG animation (short for Computer Graphics Animation) is basically something animated entirely computer-based, such as Toy Story or even video games.

Sonic and friends have been in computerized graphics.

Computer Graphics
While there have been many movies that used computer graphics animation (such as Beauty and the Beast, Aladdin, The Lion King, and Pocahontas), in 1995 Toy Story was the first completely computer-animated feature film in the history of motion pictures, with "remarkably realistic animation of startling depth, dimension, and style", with A Bug's Life to follow. Dinosaurs was the first to use real backgrounds and computer generated dinosaurs. Actually, it was Jurassic Park, but unlike Jurassic Park, Dinosaurs managed to stay in the realm of their time rather than using humans being eaten. Rather, Dinosaurs used personification to give the dinosaurs a character. Also, Computer Graphics Animation is where the future seems to be headed, with cartoons such as Reboot around. Basically, computer graphics animation has been done on normal animated features but then evolved into it's own genre.

This was state-of-the-art at one time.

Video Games
Believe it or not, video games are a medium that have some type of animation in the game, whether it's simplistic or detailed. Intricate designs of characters have varied from video game to video game, whether the environment is bright and happy like Mega Man (1987) or dark and scary like Legacy of Kain: Soul Reaver (2000). The first record of a video game was established with the game Pong (1958), created by William A. Higinbotham, where one ball goes from one side to the other. While the mechanics are extremely simple compared to today's standards, the objects are still animated nonetheless. Later, developers strive to better video games in terms of presentation and graphics, so it will appeal to the market.

Remember the days where it was you were a Nintendo fan or you're uncool? That's around when video games would take their next step. You could now explore huge worlds, go into pipes, smash turtles, and save a princess. Everything was pixel-based until later things evolved into polygons (where the first polygonal game was made in the mid 1980s). These days, there are video games such as Shenmue and Luigi's Mansion, which were all breakthroughs in the video game industry, giving the world a new style that video games can be dead serious or lighthearted. You control the character, and you're one with the character. That is the magic of all animation- on the screen you see a character you will relate to and know their feelings. Video games take animation a step farther- instead of watching the character, you are the character.