Animations:

Animations have many different forms and components. They all have a Visual component and some have audio as well.

Visual:

    Many animation styles use Keyframes which are set frames in a timeline that the artist / animator creates manually. The frames in between can either be generated or the animator can choose to draw all frames of the animation. Some more advanced software can use simulated physics to create all frames of an animation, like blender for example can use particle physics to create smoke and fire effects as shown in the video below.

Audio:

    Most animations will come with audio to make things more interesting, however it's not always required as many animations in presentation software don't include audio. 

Rendering:

    Most more complex animations have to be rendered into a single file for viewing, this does not include built in animations for presentations. This compiles the frames and audio into a readable format for the computer to play together. The below was created using Blender and rendered on my system.