Routers, Switches, Hubs, Servers, Clients and NIC's.
A router is where all the data traffic comes through. The router does what it's name states, where it determines the destination and routes data transferred to it. After it knows where your intended destination is, it will process data back towards your computer, allowing you to access your site. The speed this happens is very dependent on two things: the network's traffic, and your cable or wireless connection. If we say that you are the only user requesting data to the router, but have a standard CAT5e cabled connection, you will get an average loading speed of the webpage. Let's take the same scenario, but say you have a fibre-optic cable connected. Now, you have single-handedly the fastest connection possible, but it could be faster with the tweaking of the system and the main processing area. Wireless routers do exist, but it is a pure fact that Wireless connections are slower as there is always possible interferences.
Switches are used to combine networks. You can use them in hosting, where the data needs to be transferred to simaltaneous servers which will store it for other people to view. For example, if you had a server rack hosting many different sites, and needed to have a fall back network, you could use switches to trasfer the given data from server rack 1 to the backup server rack. Let's say you were using a server to host your website. You would connect a switch to the server to store it in a dedicated back up server. This would work, but you would need to setup the switch, so that the data transferred to the switch through whichever port will go to a port, where that port will be connected to your back-up server. You are limited tothe amount of ports, but area able to get more than one switch connected to a server.
A hub allows you to connect multiple wired ethernet devices to a single access point. This is mainly used in family homes, but can be used in small offices. The hub does not connect directly to the internet, but it does process various different connections which will allow multiple users to browse the internet at the same time. Traffic is a large issue, as a 4 port hub, and 4 people heavily using the internet will slow down the download/upload speeds as there is a lot of data being transferred via a single output/input cable. You can connect this hub to a switch, which can be connected to a router, or access point (for wireless connections), and a server. This is turn can save all of the browsing history, and allow the server to notify admins of any infiltrations in the system.
A server is practically a computer. You can connect a computer (with a monitor, keyboard, and mouse) to use the server to its maximum capability. The server can process, store and acces data, which can be very useful when used with fibre-optic connections. If the server is modern, it's technology will probably be able to process greater data, and provide an up-link to the network you can host on the server. As the server is like a computer, it has to have RAM, which, depending on how heavy data processing you intend to host, you will need a good amount. It can have a connection to an access point, allowing it to communicate with other servers which are in another room, or another building. Servers are very easy to tap into, and if they are connected to a switch or hub, an infiltration is very easy if you can get close to the switch, or the server directly.
A client is a piece of hardware, or an application which allows the server to communicate with other servers, or other computers which have the ability to carry out the given request. Any server uses a client if it needs to connect to a different server or computer, which is not close by. For example, if you were hosting a server on a powerful PC, a popular application is a VPN software by LogMeIn; Hamachi. This application allows your hosted server to connect to other computers or servers, which is very handy when people are not in your Local Area, or have no connection to your private home network.
Network Interface Cards allow things like a Sky Box, a Virgin Box, a BT Vision, or your TV to connect to internet based channels. Nowadays with the modern technology at our service, a lot of big channels like ITV or the BBC host private servers which your NIC can pick up and stream the broadcast to your home. NIC's are mainly used in PCI-e slots, and if you have a spare PCI-e slot, and want to watch TV on your computer, you can connect yourself to the channel based channels, and watch TV! I wouldn't recommend this if you have a laptop.