An animation is a series of hand drawn or digitally drawn pictures that when put together and played at a certain speed, create movement.  Some different types of animation would be:

Traditional animation: is a very old form of animation, starting in 1908. Traditional animation is often drawn on paper, and colored on paper as well. A good example of traditional animation would be the Walt Disney films, "Snow white", "Fox and the hound", and "Sleeping beauty". Other studios have also specialized in traditional animation, like Warner Bros making "looney Tunes" and Fleischer Studios making "Popeye" and "Betty Boop".

Stop motion animation: is a form of animation that uses puppets or other objects to make animation. Stop motion is often very time consuming work, having to move the object of puppet for every frame and make sure movement is as smooth as possible. They often even have to help animate the hair, and facial expressions, on the same puppet. A good example of a stop motion animation would be the movie "Coraline" by Laika Studios.

Claymation: Claymation is a form of stop motion, but it uses clay instead of a puppet or object. Claymation is also a very time consuming animation form, taking time to mold the clay character's pose, facial expression, hands, and any other part of the character. A good example of Claymation would be "Pingu" by Pingu Film studio and "Walace and Gromit" by Aardman Animations.

2D animation: can be animated traditionally or digitally. It's just drawn in a 2d form.

3D animation: is animated online in photoshop or CGI. 3d animation is an animation style done digitally to look 3d and pop out on the screen as if it was real. A good example of 3d animation would be "Toy story" and "Luca" by Pixar Animation Studios.