Sessions

I am not familiar with the concept of sessions during a web browse. = From what I gather, its just another way of passing information without = using GET and POST all over the place. The PHP docs are scanty, I guess they figure I'd know what this was. Will one of you point me toward a useful site with information on the = five W's, (who, what, when etc..). Does PHP do WinNT authentication on = its own? If not, anyone have a suggestion? I'm ok with generating content and programming--I just never bothered = integrating with LANs and WANs and other things. Thanks in advance RDB