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Cache is the word used for your browser's memory of the web pages you visit. When you browse the Internet as pages, certain pages are stored in the cache. When you revisit those pages, they can then be called up from your computer's memory, saving you time when surfing.

If you're away from your phone, or your phone's not working, this handy tool sends your incoming calls to another phone, either mobile or landline. You can divert any or all of your calls to anywhere in the UK and to most overseas destinations.

The set of numbers you choose for your Friends & Family discounted calls is called a Calling Circle. Find out more about Friends & Family

Your card security code (CSC) is a unique three or four-digit number that offers you an extra level of security when you're using your credit card. As the CSC appears only on the card (not on receipts or statements), it provides some additional validation that the card is actually in your rightful possession. The CSC is usually printed on the back of your debit or credit card (usually in the signature field) although on American Express cards, it is printed on the front of the card, to the right and slightly above the raised credit card number. On some cards, where the CSC is placed in the signature field, all or part of the card number appears before the CSC. For example, if the numbers 6789 123 appear on the back of your card, 6789 is the last four digits of the card number and 123 is the CSC.

BT Chargecard is a card that enables you to make calls from virtually any fixed phone which are then charged to your business or home phone account. You then pay for your calls by credit / debit card or by Direct Debit.

Once a fault has been repaired, we remove it from our active file when you let us know that you're satisfied with the repair. If we haven't heard from you, the fault is closed 7 days after we've repaired it.

A cookie is a piece of information that some websites create when you visit them. When you sign up and create a profile with BT.com, we create a cookie on your PC. This stores some information about you and helps us identify you when you next log in. As a result, we can provide you with more relevant content. The cookie we create only contains basic information such as your log-in name, we do not store details of your phone number, account or payment details in the cookie.

The names and numbers you put in your Address book are known as contacts. If you phone any of your contacts, your bill will show their names as well as the numbers, so you can see who you've called at a glance. Find out more about the Address book.

BT's Continuous Card Recurring Authority is a convenient way to pay your whole bill monthly by credit or debit card. Payment will be taken automatically on the day stated on your bill. If you currently receive a quarterly bill you will need to change to monthly billing in order to use Continuous Card Recurring Authority. Should your credit or debit card number change you will need to notify BT of your new card details.

This is the name of a report or graph that you can make, displaying your calls by how much they cost. When you sign up to manage your account online, you can access graphs and reports to show your calling patterns in an easy-to-read format. You can choose to display your calls by duration or cost, as well as specify the range of dates included in the graph.

CSV stands for 'comma separated value' and is a certain kind of file. When you sign up for online billing, you can download your bill information as a CSV file. This makes it easy for you to transfer the information on your online bill and import it into applications like Microsoft Excel or Microsoft Word. Find out more about online billing.

Your CV2 number is the number printed on the signature strip of your credit or debit card.