What is a statistics cookie in Org mode and what is their use?

Question

I am learning to use Org-mode. The manual mentions that command org-ctrl-ctrl-c works depending on the context. One of the examples is that if the cursor is on a statistics cookie, it updates it.

What is a statistics cookie? Are there other kinds of cookies? Is the concept of cookies general to Emacs or specific to Org-mode?

I am still learning so I apologize for this naive question but I asked only when searching on DuckDuckGo and Google did not produce a satisfactory result. One result did offer some clarification but I wanted more. That link is http://iso.mor.phis.me/projects/mlorg/docs/SYNTAX.html#Statistics_cookies .

Answer 1

In this org file:

* TODO Organize party [2/4]
  - [-] call people [33%]
    - [ ] Peter
    - [X] Sarah
    - [ ] Sam
  - [X] order food
  - [ ] think about what music to play
  - [X] talk to the neighbors

The [2/4] and [33%] are statistics cookies. They describe the completion status of the children of the thing they're on.

They're pretty useful, because they update automatically as you update the status of children. You can also use them to show the status of child TODO tasks:

* TODO bake a cake [3/6]
** DONE buy ingredients
** DONE start cooking
** DONE realize you forgot eggs, dammit
** TODO drive back to the store and buy eggs
** TODO wait, I needed THREE sticks of butter?
** TODO drive back to the store and just buy a damn cake

Some more information is here. I also pulled the example org file above from that page.