I can't visualize in my mind the network traffic flow. eg. If there are 15 pc's in a LAN. When packet goes from router to local LAN, do it passes all the computers? Means did it goes to ehernet card of every computer and those computers accept the packet based on their physical address. To which pc the packet will go first? To the nearest to the router? What happen if that first pc captures that packet(though it is not for it)? What happens when a pc broadcast a message? Do it have to generate 14 packets for all the pc's or only one packet reach to all pc's? If it is one packet and captured by first pc, how other pc's can get that?

I can't imagine how this traffic is exactly flows? May be my analogy is completely wrong. Can anybody explain me this? Thanks in advance.