An identity card is used to prove identity, generally in the issuing country. It can be used as a travel document if agreed between countries, as is the case among European nations.
Several countries still issue identity cards that do not comply with the ICAO’s Document 9303 standard, but the trend is towards delivering identity cards in a credit-card-like format that respects the standard.
In Europe, identity cards exist in all EU nations except Denmark and the United Kingdom. Among those that have implemented it, only Austria, France, Italy and Lithuania have not made it mandatory. In Portugal, a single card serves as an identity card, social security card, taxpayer card and polling card.
An optional identity card exists in the USA: the US passport card, which is not widely used. As a driving licence is widely used as proof of identity in North America, some states have opted to issue identity cards for non-drivers that have the same characteristics as a driving licence.
Securing this document is a common concern for all countries. Arguments put forward to justify reinforcing it revolve mostly around security concerns: population movements, terrorism etc.