http://vjump.shueisha.co.jp/battle-survivor/049/index.html

The video is in Japanese, of course. Some people just prefer a more visual approach.

No new information is added: “Pendulums are half monsters/half spells, they have pendulum effects, they have Pendulum Scales, you Pendulum Summon using two, refering their scales, once per turn as many monsters as you like, you can also SS a Pendulum in your Extra”.