What is promise? Is it part of Protractor or AngularJs or Javascript?

I am recently learning about Protractor that is used to automated testing of angularJS. All the tutorials I see online the word "Promise" seems to pop up. I am new to automation and have no idea what this means. I have looked around on web but did not find a good answer. Is "Promise" a Javascript thing or Protractor thing?

If you look at this link: http://ift.tt/2o3GgzF the word promise is used "Since all actions are asynchronous, all action methods return a promise. So, to log the text of an element, you would do something like:"