PBX
Private Branch Exchange. This is traditionally a hardware device that routes calls in an office telephone system. IP PBX refers to the IP based call management server used in VoIP installations.

VoIP
Voice over Internet Protocol. This is the terminology to describe the routing of voice calls over the Internet, whether they are propriety (e.g. Skype) or open (e.g. SIP).

CMS
Content Management Systems is a way in which businesses can easily manage their content inhouse. Content can be edited or updated via a user interface that is provided by the application develiver the CMS.

Switch
Network device which switches traffic between two hosts.

Router
Network device which determines which route to direct traffic to reach its destination. Routers often have interfaces to different networks, e.g. one interface to the office network, and another to the ADSL connection and a third for backup dialup, etc.

ADSL
Asymmetric Digital Subscriber Line. Your standard analogue line is split, so part of it is used for data, and the rest for voice calls. This allows for great download speeds, but upload speeds are much slower.

SDSL
Symmetric Digital Subscriber Line. Similar to ADSL, except the whole channel on your analogue line is used for data, which means upload and download speeds are equal.

SSL
Secure Sockets Layer. Technology used to encrypt web pages so attackers cannot intercept communication between your browser and the web server.

BLOG
Blog is the term that stands for weblog. It is essentially a website that allows for regular entries, like a diary or journal. A blog can contain text or images or both, there are no real restrictions.

DDI/DID
Direct Dialing In/Direct Inward Dialing - This describes the ability to route a call directly to an telephone extension, without the call having to be filter either via an IVR application or receptionist.

IVR
Interactive Voice Response - This the telephone application that allows a user to interact with an auto attendant. When you retrieve your voicemail, you are calling up an IVR application.

SEO
Search Engine Optimisation is the process to improving the ranking of a website within a search engine so that it is exposed to more users. There are methods and techiques to do with content and website design that will help improve your website ranking in search engines.

MPLS
Multi Protocol Label Switching is a technology to improve traffic on your network. Each data packet is assigned a label to identify what kind of traffic it is (Web, email, IM, gaming, etc). The routers on the network then uses this information to determine the priority. This enables Service Providers to guarantee quick delivery on certain types of traffic (e.g. VoIP).

PSTN
The Public Switch Telephone Network is the telephone network as it is traditionally know. When a caller dials a number, the call is switch through different circuits until it reaches its destination. BT is currently busy replacing this network with an IP (VoIP) based system, in a project known as "21CN".

ISDN
Integrated Services Digital Network is a digital telephone line (as aposed to the normal analogue you may have at home). The advantage is that one line can be split in different channels, so you can have multiple "lines" over one physical telephone line. In telephony, you would normally have either a ISDN2 or ISDN30 line. The 2 and 30 refers to the maximum number of "lines" or concurrent calls you can make.