What is Network Adapter?

A network adapter interfaces a computer to a network. The term "adapter" was popularized originally by Ethernet add-in cards for PCs. A network interface controller (also known as a network interface card, network adapter, LAN adapter) is a computer hardware component that connects a computer to a computer network.

Modern network adapter hardware exists in serveral forms. Traditional Ethernet adapters for desktop PCs were PCI cards. PCMCIA (also know as "credit card" or "PC card") adapters or similar devices that connected to USB ports were more commonly used in laptop computers. Nowadays, though, both Ethernet and wireless network adapters are simply integrated circuit chips pre-installed inside the computer.
Most Network Interface Cards are designed for a particular type of network, protocol and media, although some can serve multiple networks.
While network interface controller implementation expansion card inserted into the computer bus, the low cost and ubiquity of Ethernet standard means that most new computers with network interface on the motherboard.
It allows users to connect to each other or through the use of cable or wirelessly if the NIC is a wireless NIC (WiFi/WNIC). Each entity in the network, computers, printers, routers, etc., needs and other equipment must have a network card if it is network communication. In the old computers, network card may be an expansion card, usually PCI or serial bus.
High performance card can speed less that $30. NIC functionality is now often integrated into the motherboard chipset or implement with a dedicated Ethernet chip on the motherboard.
A similar situation applies to laptops. At the same time, a PCMCIA network card would be used in a laptop computer for the NIC just as the PCI card was used in desktop computer, but now, the function of the card is usually combined with the motherboard.
Ethernet is the dominant standard for cable connections for wired computer networks. An Ethernet connector looks similar to telephone, only larger. This connector is called RJ45 connector. Ethernet cable are either a shielded or unshielded cable of four twisted pairs of 24 AWG connectors, specified in the impedance of 100 ohms. Maximum cable length for CATX cables is 100 meters.
Early versions of Ethernet cable is CAT3 or CAT4 (CAT is referred to as "category). These versions were not long lived. Cat5 and Cat5e are currently the most commonly used cables, with Cat6 available and the configuration of the near-future. A cat7 cable specification is in development, and should be available in a few years.
Each Ethernet NIC has a unique serial number called "media access code" (MAC address), is used to identify the network adapter, and associated computer on the network. No two NIC will have the same address, because the NIC manufacturers must purchase blocks of addresses from the Institute of Electrical and Electronics Engineers (IEEE).
The NIC card are capable of different speeds. Speeds of up to one gigabit per second (Gbps) are now available. Two NIC can communicate if they differ in speed ratings, but they will communicate at the rate of the slower NIC.
An Ethernet network controller typically has an 8P8C socket where the network cable is connected. Older NICs also supplied BNC, or AUI connections. A few LEDs inform the user of whether the network is active, and whether or not data transmission occurs. Ethernet network controllers typically support 10 Mbit/s Ethernet, 100 Mbit/s Ethernet, and 1000 Mbit/s Ethernet varieties. Such controllers are designated 10/100/1000 - this means they can support a notional maximum transfer rate of 10, 100 or 1000 Megabits per second.
On a very simple network, NIC can be used to link PC. If the computer is directly to one another, the network is a "peer-to-peer" network. If computers are connected directly to one another, a "cross-over" Ethernet cable is needed. This cable is not "straight-through" like standard Ethernet, but crosses the send and receive connectors, so that send line from computer A connects to the receive line of computer B.
For networks of a few computers, a "hub" can be used, with all of the computers connected to the hub. Any message sent from any PC will be seen by all of the computers, but only the computer with the correct MAC address will receive the message. P2P networks are useful for many purposes. File and printer sharing are the most common applications.