cookies

can somebody explain me how to use cookies i know how to use javascript javascript:alert(document.cookie) and i get some cookies but i think these are mine cookies and i also have web developer for mozilla and i can also see cookies but i think they are also mine so i was thinking maybe i have to change them but big question is how what to write and how to find admin cookies

yes it will help me in some challenges like in pen-testing but i want to learn how to do this i was reading a lot tutors on this site i googled a lot but nothing can you teach me how to do this because it is useful i think i need to make new cookie but what to type in that is problem how to find that cookie (admin cookie maybe) please teach me:):)

but how to do this do you know