Poland A and B
Poland A and B (Polish: Polska "A" i "B") refers to the historical, political, and cultural distinction between west and east areas of Poland, with the west (Poland A) being significantly more economically developed, but growing less quickly than the east (Poland B).
With respect to religion, Poland B is more traditionalist and inward-looking, taking its lead from the church; while Poland A is more cosmopolitan, tending to see Poland as a part of Western Europe.
The distinction is unofficial and in some ways oversimplifying, but it is nonetheless widely understood within Poland. It can be thought of as analogous to the "Blue State/Red State" divide in American politics. (Here Poland A would be the Democratic-leaning Blue States; and Poland B, the Republican-leaning Red States.)
After a 2010 plane crash took the life of president Lech Kaczyński, his wife, and dozens of Polish dignitaries, the country briefly came together to mourn. But the underlying fissures, mutual suspicions, and ugly recriminations between Poland A and B soon resurfaced.
Historically, the source of Poland A and B can be traced to the period of the partitions of Poland, and different policies of the partitioners, which resulted in a much larger industrial development of the Western Prussian partition.
At the moment, the development of Eastern Poland runs faster, than western. The western provinces (except Lower Silesia) have slower growth of the GDP and higher level of unemployment than eastern Poland. Several cities in the Eastern Poland have very good economical situation and level of development (e.g., Olsztyn and Rzeszów are on the top of rankings estimating living standard)[dubious ].
In this East - West differentiation has to be recognized that Poland's borders moved westward after 1945. For example Warsaw was historically in the developed western part of Poland and now is situated in the eastern part of the country. The slower growing western provinces are often former German regions now populated mostly by Poles from the former Eastern Polish regions. For example the above mentioned Olsztyn was part of Prussia after the partitions of Poland. So the "heart" of Poland has not changed so much.
See also 
- Amy Drozdowska-McGuire, reporter: "Solidarity For Never", originally broadcast on Public Radio program "This American Life", Dec. 16, 2011.
- Kozak M., Pyszkowski A., Szewczyk R. (red.) 2001, Słownik Rozwoju Regionalnego, PARR, Warszawa.
- Polska Polsce nierówna, 2008-06-04
- Gazeta Wyborcza (1999) 'Polska A, B i C' (Poland A, B and C), August 4