Network Interface Controller/Card (NIC)

NIC or network interface card or network adapter, LAN adapter is an important  hardware requirement for connectivity . Actually this interface  card provides us the 'gateway' through which data from one computer A can be transfered to another computer B. Its somewhat the  same as normal gate that we use in daily life to enter and exit.
A NIC technically is network adapter hardware in the form factor of an add-in card such as a PCI or PCMCIA card. Its actually a stick( looking somewhat like ram) and is mostly having an RJ45 connector at their one end.( u can see it at the back of ur laptop or PC..its where ur Ethernet wire is attached). Here is an image of what NIC looks like:

NIC is OSI layer 2 device (DATA LINK LAYER U can see this for more osi blog) . its consist of factory fitted 48bit address similar to that of ip address, here its called the MAC address or the Media Access Control address which is in .human-friendly form, is represented in  six groups of two hexadecimal digits, separated by hyphens (-)  or  colons (:), in transmission order.
For example ,consider the following

• 01-23-45-67-89-ab

•  01:23:45:67:89:ab

•  0001.4202.8360

the last one is not used much now days.