ADSL
This is an abbreviation of Asymmetric Digital Subscriber Line and the term is used interchangeably with “broadband”.  ADSL is a data communications technology that allows for the faster transfer of data across standard copper telephone lines than a conventional dial up modem can manage. ADSL provides a high speed, always on connection that can carry both data and voice.  The term “asymmetric” is used because the data being carried along the line moves faster one way than the other. In other words, downloading is faster the uploading.

Bandwidth

This is a term dictating how fast you can send and receive data using your connection.  A standard analogy is to imagine your Internet connection is a pipe, the wider the pipe, the faster the information will pass through.  Contention ratios are important when evaluating bandwidth.

Burstable

The ability to increase the throughput of your broadband connection for determined times should you require an increase in speed. For example, if you are downloading a large file.

CAT5                     

Category 5 is a type of network cable.

CBT

An acronym for Constant Bit Rate.
CHAP

An acronym for Challenge Handshake Authentication Protocol.
Contention Ratio

This describes the maximum number of users sharing the bandwidth on the broadband connection between your local exchange and your broadband provider.  Standard contention ratios are 50:1 and 20:1. If you had a 50:1 connection ratio it would mean that at any one time you would never be sharing your bandwidth with more than 49 other users. Therefore, the lower the contention rate the better.

CRC

This is an acronym for Cyclic Redundancy Check.

DACS

An acronym for Digital Access Carrier System.
DHCP

An acronym for Dynamic Host Configuration Protocol.

Dial Up

Dial-up Internet access was the original method of connecting to the Internet for the mass market via connecting by a phone line.  Transfer speeds were a maximum of 56k and it was not possible to connect to the Internet and make telephone calls simultaneously.

DNS

An acronym for the Domain Name System.

DSL

DSL is an acronym for Digital Subscriber Line.  This is a method of transmitting data over telephone lines prevalent in the United States. The UK uses a variant called ADSL for providing broadband to users.

DSLAM

An acronym for Digital Subscriber Line Access Multiplexer. This is a function that aggregates broadband connections into one main link on the Internet backbone. 
Dynamic IP address

This is an IP address that changes each time you connect to the Internet.

Encryption

Encryption is a method of hiding content from non-permitted users. Only permitted users will have the correct key to unlock the content. An example of this is PGP (Pretty Good Privacy) a popular program for typically encrypting email messages.

Ethernet

Ethernet is the most popular form of local area network (LAN) technology.

Extranet

An extranet is essentially an intranet that can be accessed by computers outside the network but is not available to the general public.

Firewall

A firewall can be implemented through hardware or software and will help to prevent the unauthorised access of your computer by unauthorised users.

Gateway

This is another term for router. See router definition below.

Gateway address

This is the IP address used when a connection outside your network is commenced.