Does GM_xmlhttpRequest access the website as if I am accessing the website in my browser?

I am curious as to how GM_xmlhttpRequest() reads a page in certain situations.
Does GM_xmlhttpRequest access the website as if I am accessing the website in my browser?

Do sessions remain valid? For example: If I log into a website from one browser tab and then, from another tab, I send a GM_xmlhttpRequest from my script, is this new request also logged in?

One reason I ask is because at one point in my script I am sending a GM_xmlhttpRequest to one of my domain's pages that reports back the REMOTE_ADDR from PHP. This is reporting back my computer's IP (which is what I want) instead of the page I am calling this function from.

OMG it totally does!!!!!!

var server2="http://www.somesiteimloggedinto.com";
var test_data=function(){
    GM_xmlhttpRequest({
        method: "GET",
        url: server2,
        onload: function(response) {
            if(response.status == 200){
                alert(response.responseText);
            }
        },
        onerror: function(response) {
            console.log("Connection to "+server2+" failed.");
        }
    });
};
test_data();