NB: I've subsequently edited this post to respond to Angry Guy's response question. Click View Entire Answer to read it (scroll down to the bottom). A router allows multiple devices to access one point of connection (such as an ADSL connection if the router's an ADSL router with a built-in ADSL modem, an uplink to the Internet if being used on a network, or another computer being used as an upstream proxy server). Routers commonly have DHCP servers installed, to provide connected devices with an INTERNAL ONLY IP address on a private subnet range. This means that whilst the internet will see only one requests from one IP address (the outward IP address of the router's ethernet adaptor / adsl modem), the router's routing table, combined with the abillities of the DHCP server, can cope with multiple requests to various sources (web sites, gaming servers etc), routed through the one external connection, but separated out and correctly distributed to the various connected devices. An access point is a wireless version of a switch - it's a much simpler device, similar in function to a router, but with no DHCP server - it merely acts as a pass-through for multiple devices to transparently connect to (and share) a single uplink or other connection. As switches contain no DHCP server, they can be connected to a router to provide a) extra connectivity, and b) further network availability reach for wireless devices. A gateway is (typically) a hardware device, or possibly a computer, that provides access to some upstream network and then offers and distributes it down to machines connected to it. In essence, imagine a gateway device as the doorway between a larger network (say, the Internet) and a more local, private network (such as a corporate intranet). The gateway may also double as a firewall, restricting inbound access to unauthorised resources, providing NAT access to authorised end-users (e.g. employees of a company who wish to check their internal email while at home can connect through the firewall with a username and password to access this otherwise-internal content), and filtering incoming access to external resources, such as a proxy server with content filtering would provide. This can allow an employer to block or filter Internet access, so employees can continue to use the Internet for work-related purposes, but can't sit around on MSN Messenger all day instead. Cruel, but true. A (network) bridge allows you to connect two or more segments of a network, or even two or more networks (be they wired or wireless) together, to make one larger network. Microsoft Windows operating systems can do this, provided that all the networks are connected to the machine that you wish to use to create the virtual bridge upon. You can also buy hardware to achieve this end without having to rely on a computer to do the job for you, although this will be (obviously) more expensive - but more reliable, once it's configured properly. Not to be confused with a router, a bridge can only connect together existing networks that you have access to. A switch can also perform this task, but I tend to think of a switch as more of a connectivity-expansion device and not a dedicated bridge device. More information on this subtopic can be found on Wikipedia at http://en.wikipedia.org/wiki/Network_bridge . HTH, Christopher. Appendix 1: Hungry Guy: Suppose I wanted to keep my kid from going to porn sites, would I use a router, or a gateway, or both? Me: You could use a router to do this, as some manufacturers provide a simple content filtering service. I believe that a couple of manufacturers include a (possibly time-limited) subscription to Internet Filtering services, which you can use to filter content that you deem to be inappropriate. A much safer bet would be to install software that filters content locally, on your computer, this is usually accompanied with a paid subscription, but you can be certain of almost 100% inappropriate filtering, whereas with routers you can do things such as add individual sites to the block lists on the router, but obviously adding hundreds and thousands of URLs of inappropriate content will take a loooooong time. Much simple and time-effective to subscribe to an external service, as they have much more time to update their lists of inappropriate content and serve them out to their subscribers.

Chris' answer was excellent, but I would like to clarify some things as part of my own answer. Router - Chris' definition is actually for one kind of router, a Network Address Translation (NAT) router, the kind you can use to share an Internet connection between multiple computers with. A true router simply allows for hosts that are not on the same logical network, like an IP subnet, to communicate with each other. The router receives packets (chunks of data) on an interface and routes them to where they need to go based on a routing table; the table allows the router to have knowledge of where a given logical network is located. The router operates at the network layer (layer 3) of the OSI model. The OSI model separates all of the "under the hood" workings of network communication between two hosts via several layers that represent different functions. Understanding the OSI model is crucial to understanding the difference between routers/gateways and bridges. Gateway - As I said in my answer to the question posed in http://www.answerbag.com/q_view.php/10824 , this is really just another term for a router. However, the definition that Chris gave is still a good one. Bridge - This device operates at layer 2 of the OSI model and allows hosts on different physical network segments (as opposed to logical networks) to communicate with each other. The bridge is not aware of what goes on at layer 3 and forwards layer 2 frames based on a bridging table that tells it where a host on a segment is located relative to the bridge. A switch is simply a multi-port bridge.

hello i want to know how to make a wireless connection between access point and router.

Wikipedia banned at your location, I take it?