Their populations do not see themselves as Eastern Europeans, and many consider it a pejorative term. Most countries prefer to include themselves in other groups, associating themselves with Germany in Central Europe, with Scandinavia in Northern Europe or with Italy and Greece in Southern Europe.
As a term its origins are fairly recent. For many years Europe was divided on a North South axis. With the southern Mediterranean states having much in common, and the northern Atlantic Ocean and Baltic Sea bordering states also having much in common. The term first arose in the 18th and 19th century and to describe an area that was falling behind the rest of Europe economically. It was seen as a region where serfdom and autocratic governments persisted long after those notions were fading in the west. It was always a very vague notion, however, and many countries in the region did not fit the stereotypical view.
Much of Eastern Europe has ties to both the east and west. While all of the countries were heavily influenced by Roman Catholic or Protestant Christianity and have very close historical and cultural ties to Germany, Italy, France or Scandinavia (e.g. the Hanseatic league in the Baltics), many countries also had relations with the East. Russia was under the control of the Mongols for centuries and inherited political and social conventions from them. Further south the Ottoman Empire and Islam had a very strong influence. The nations of the Balkans as well as Hungary and Romania were all at one time controlled by the Turks.
The concept of Eastern Europe was greatly strengthened by the domination of the region by the Soviet Union after the Second World War and the takeover of the nations of the region by communist governments. The idea of an "Iron Curtain" separating Eastern and Western Europe was an extremely common view throughout the Cold War. This strict dualism caused problems, however, as it failed to account for the complexities of the region. For instance, Yugoslavia and Albania refused to be controlled by Moscow, but this division was often ignored by many in the west.
The countries normally meant by the term Eastern Europe are: