Eastern Europe is a subregion of the European continent. Wikipedia

Eastern part of Europe Wikidata

A geographic region of the European continent west of Asia and east of Germany and the Adriatic Sea, traditionally consisting of countries that were formerly part of the Soviet Union, such as Poland, the Czech Republic, Slovakia, Hungary, Romania, Serbia, Croatia and Bulgaria. OmegaWiki

A socio-politic geographical area of eastern Europe usually including the European countries to the east of Germany, Austria and Italy, and to the west of the Urals. However, a less common definition of the region excludes the Czech Republic, Hungary, Poland, Slovakia, the Baltic states and some parts of the Balkans - placing them in Central Europe instead. Wiktionary

Eastern Europe. Wiktionary (translation)