Networking is the act of grouping computers or devices such as printers together by means of media (cables, wireless, etc) that allows communication.
For home computing, wireless devices are fast becoming commonplace for connecting devices without the need for running cables.
A device attached a LAN must be equipped with a Network Interface Card (NIC) more commonly known as a network card. Most Motherboards now have at least one NIC connection built-in. Older computers (ones without a NIC integrated into the motherboard) need an add-on NIC to connect. The network card will typically be a 100MB Ethernet connector, newer PCs will probably include a Gigabit connector.
Switches
A switch connects computers and other devices together on a local area network (LAN). For example, if there are four PCs
to be networked, each with its own NIC, then each PC is connected from the NIC to a port on the switch by a network cable.
The switch acts as a communications hub and physically connects the devices to the LAN.
Hubs
A hub is similar to a switch, but is a simpler device. A hub merely connects your devices together at the physical layer,
wheras a switch not only connects the devices physically, ot also has the capability to filter or forward Ethernet frames
based on their intended destination on the LAN.
Router
A router is a device that allows computers to communicate from network-to-network. It forwards packets based on their
destination. This is similar to a switch, but on a grander scale. A router is more intelligent than a switch--switches
aren't aware of differences between networks, whereas routers are. Routers maintain "routing tables" which contain
information on the locations of other networks. Routers use the routing table to determine the best path to send data
along to its final destination.
Wireless Routers/Switches
Most modern home wireless access points are a combination of a router and switch. If your
wireless router has multiple
ports that can be used to connect your wired network devices to your wireless network, then your device most likely has
integrated switch functionality. If your wireless access point acts as a gateway (sitting directly behind a cable or DSL
modem) then it's almost definitely performing "router" duties. There's also a good chance your device has a rudimentary
firewall function protecting your internal network from unwanted intruders lurking beyond your cable/dsl modem.