They're asking about the OSI model. Layer 2 is the data link layer. Ethernet uses data packets called frames to ID and establish the physical (MAC or EUI) address of the laptop. More at http://en.wikipedia.org/wiki/OSI_model#Layer_2:_data_link_layer

That's a stupid question. How would knowing the answer help you do that job better? You probably learned that 10 to 15 years ago and don't remember. You don't have to remember as you can always look it up. Is this a show about knowing more than a 5th grader?