Can someone explain what an AuthenticationSession is exactly and what would be an example of an AuthenticationSession object?

I couldn't find any references to 'AuthenticationSession' in Kratos. Where did you stumble upon it?

In fact i noticed it on oathkeeper https://www.ory.sh/oathkeeper/docs/next/pipeline#session but i was thinking maybe its related to Kratos

Oh, now that makes more sense. I'm not currently using Oathkeeper, but my best guess is that it lets you access information extracted by the authenticator (and it doesn't matter whether it comes from a cookie, jwt, or something else)