How to easily design animation using html

Question

HTML

Answer 1

<svg>, <canvas>

Answer 2

In order of easiest: Css3 animation, Svg animations, JS animations...
The three can be mixed, and 'easiest' not means 'easy', just less difficult, and may widely depends on context ( what you want to do, what you already know, and so on... for some people, learning JS will be less obscure than understanding deeply CSS to correctly handle animations ) :P