This is how it's done.
Go to some site, let's say facebook/netflix .
Check out the cookies that the site uses to authenticate you, you can edit the cookies from the dev tools! just mess around with them, edit them until you refresh the page and you are logged out, try to figure out what are the cookies that hold your session ID.
In facebook's case the cookies that are required are called "c_user" and "xs"
if you open a diferent browser (say firefox) or a diferent computer and paste those cookies while you are on facebook's domain using the dev tools, then you will be able to resume your previous session, that's session hijacking
You can add cookies on firefox on the development tools, under storage, by pressing that Plus button.
Facebook might complain, because it will see that you suddenly changed the user agent (or some other way of fingerprinting who you are) and will likely send you a notification asking about "suspicious activity" on your account.
The "cookies" file you mention is a SQLite database that contains ALL these cookes, you can open it with sqlite browser and check them out yourself. The actual values of the cookies have been encripted in recent versions of chrome, so they cant be viewed from the sqli database so easily.
A few ways of getting the content of cookies from someone else are:
If the cookie is sent over HTTP instead of HTTPS and you are in a shared wireless network, you can sniff the traffic and get the cookie
After you have the cookie, you just insert it into the browser as shown above and you are done.
Usually important cookies are marked with the parameters
- secure - It can only be sent over HTTPS
So they are much harder to steal.
For more information on cookies you may want to read Their specifications
Edit: just realized that this question is so old. for some reason it appeared on the site's front page.