Could some one tell me what is the difference between FastLED.show() and FastLED.delay()

Could some one tell me what is the difference between FastLED.show() and FastLED.delay()

https://plus.google.com/113564762882216741749/posts/KCxCR83GHr7

https://plus.google.com/+AndrewTuline/posts/4BUgrkWgmdj

Side note: Avoid using delay if possible.

@marmil thx lots of interesting info !!