Probably almost everybody knows that an identity card is a piece of cardboard or plastic that is shown to security guards, police officers, immigration staff.  Cards are issued by all manner of organisations: universities issue them to staff and students, governments issue them to citizens, companies issue them to their staff.  Most of these cards contain some basic details such as name, a photograph of the person's face and a reference number that allows the card to matched to some central record held by the card issuer.  Some of the more sophisticated cards also contain magnetic strips or barcodes that can be used with other machines to unlock doors so that the card acts like a key.
A biometric identity card is similar to existing cards but will also contain biometric information.

What is biometric information?

Put simply biometric information is information about a specific person's body.  Hair colour and height are simple examples of biometric information.  However for identification purposes hair colour and height are not very useful information because they change relatively rapidly (hair colour is changed by dye or by sunshine or by age; a person's height varies throughout the day according to the pressure on the spine).  For identification purposes the most well known type of biometric information is the fingerprint; these are used because it is believed that no two people have the same patterns in the skin of their fingers and the patterns are relatively constant; they might change a little as a person gains or loses weight but the patterns remain recognisable.  Another commonly used form of biometric information is DNA sequences.  DNA is the biological code that is present in every cell in the body and that describes each individual person.

How will biometric information be put on a card?

In the 21st century it is possible to store quite large amounts of information in very small spaces.  The information can be stored on a microchip on the card or on a magnetic strip.  These are the same technologies that have been used on credit cards for some years.  The amount of storage space needed to describe a person's fingerprints can easily be stored on a small microchip and that microchip can quite easily be embedded into thin plastic like a credit card — this is the same sort of technology as is used on the “chip and pin” cards that UK banks have been issuing since about 2003.
What biometric information will be stored on the card?
The government has not yet been able to decide exactly what information will be stored.  There are many issues to consider.  Whatever measurement is chosen must be something that doesn't generally change, and that can be easily provided by most people, including disabled or elderly people.  The most likely candidates are finger prints and images of the iris of the eye which, like fingerprints, are believed to be unique to each person.

How will the information used once it is on the card?

The government has not had much to say about how the information will be used.  Their silence is understandable because they know that the truth will be quite unpalatable to any sensible person who has more than a modicum of understanding of history.  Two simple facts need to be understood:
First, merely issuing identification cards doesn't achieve anything ... identification cards only have any purpose if they are checked and used to control access to places and services.
Second, the information on the card has to be checked against some other list.  Since that list will be stored on a computer it means that every use of the card can be monitored and traced and since that card is inextricably linked to you, that means that your activity can be monitored and you can be traced.
The prospective use, and inevitable misuse and abuse of the information is the reason that this web site exists and we invite you to read all the articles in order to understand fully the dangers of what the government is proposing.  Biometric identification systems are not the benign tool of liberal and socialist governments that the UK government likes to claim.  On the contrary, such systems would make an ideal tool with which to introduce tyranny and oppression and the British government is not somehow immune from such things.

Should I be concerned, and if so why?

The Labour party UK government has been pressing for the introduction for several years and has given at least half a dozen different explanations as to why they are desirable or necessary.  The UK government would like everybody to believe that biomemtric identitification systems are a good thing that will bring real benefits for the honest citizen and real problems for the criminal.
We disagree entirely.  In our opinion the creation and maintainence of the biometric identification system will be costly and complicated and will achieve none of the benefits that the government claims.  Biometric identification systems cannot prevent terrorism, they will not prevent identity fraud, they will not prevent money laundering, they will not prevent illegal immigration.
However we do not think the system is merely useless and a huge waste of money; we also think it is extremely dangerous.  In the United Kingdom peace and stability are maintained by a balance of power between the general population, the courts, the government and corporations.  Biometric identification systems shift that balance of power firmly away from the general population and towards government, and history teaches us very clearly that when the balance of power shifts too much towards government then oppression, persecution and tyranny inevitably follow.  Britain is not exempt from this pattern and if we wish to avoid tyranny in our own land then we need to ensure that the present balance of power is maintained.
We believe that biometric identification systems will create real and serious problems for the honest citizen and will be used by criminals and tyrants to their own advantage; our articles explain why ...