for those who asked what is rendering: Disney's Practical Guide to Path Tracing

…very Disney-ish, but well explained!
(for what purpose does Disney produce such a film???)

Disney has done little BTS films like this over the years. They're interesting, kept on a very simple level, just publicity. If anyone has any interest in animation, the book "The Illusion Of Life" is a must-read, for sure. Even if you just do motion graphics, this book has information that will help you bring your work to a whole new level. One of my favs.
en.wikipedia.org/wiki/Disney_Animation:_The_Illusion_of_Life

As for what Rendering is, it is many different things, even in the context of video/film/animation. Isn't the automatic "Tweening" that an NLE or motion graphics app does just another form of "rendering"?

ORIGIN
late Middle English: from Old French rendre, from an alteration of Latin reddere ‘give back,’ from re- ‘back’ + dare ‘give.’ The earliest senses were ‘recite,’‘translate,’ and ‘give back’ (hence ‘represent’ and ‘perform’); ‘hand over’ (hence ‘give (help)’ and ‘submit for consideration’); ‘cause to be’; and ‘melt down.’