Google Chrome Extension - background script

The background script is a script running in the background to handle majority of chrome events that content scripts cannot. Content scripts are purely the content of the each page. Both cannot speak to each other, however, you can give the scripts listeners (e.g. chrome.browserAction.addListener(myFunction) plays the function when the button in the top right of your screen for the extension is clicked) order to find out whether a button has been pressed or even send a message from the background script into the page's console.

https://youtu.be/ew9ut7ixIlI This video was a great introduction for me about background scripts, however, the part where he begins to talk about the listeners and such is 6:30.

The background script should be viewed as "running in the background of the Chrome browser".
Your desired effect (running a script for every page) is actually a task for content scripts.

To learn more, read https://developer.chrome.com/extensions/overview.html#arch.

The effect is produced because whenever you load chrome://extensions it forces the extensions to reload, the same behavior can be reproduced using CTRL+R. So every time, the background page got a fresh reload, which doesn't happen in case of other pages.

It is because you are using the background page .. use the event page instead by slightly modifying the manifest.json.. Try adding this:

"background": {
    "scripts": ["jquery-latest.js","background.js"],
    "persistent": false
  },

for more details on event pages check this : https://developer.chrome.com/extensions/event_pages