Meaning of SOP (same origin policy)

Question

What is the real meaning of SOP (Same Origin Policy)?

I know it means that the Javascript code from one origin cannot accuess resources from another origin. But what exactly does the word "resources" mean? For example:

1. Javascript code can access IMAGES from another site.
2. Javascript code cannot make ajax request to another side.

But when you use JSON padding, after completing the loading of a padded script tag, the 3rd party script will call your specified callback -- Javascript code from one site is invoking a method of Javascript code from another. Does this violate SOP?

Answer 1

There are several types but if we don't specify:

SOP refers to a mechanism that governs the ability for JavaScript and other scripting languages to access DOM properties and methods across domains

Here you have an excellent description of different types of SOP.