The Polish Question refers to the complicated political situation that existed in the early to mid-19th century regarding the status of Poland.
Basically, Poland had been its own country for a long time, but in the late 1700s it was taken over by its neighbors: Russia, Prussia (which is now part of Germany), and Austria. These countries divided up Poland between them and controlled it for several years, but the Polish people never really liked this arrangement.
In the 1800s, there were a few uprisings and revolutions in Poland as people tried to regain their independence. However, none of these were successful and the country remained under foreign control.
The Polish Question arose because the other European countries weren't sure what to do about Poland. Some countries supported Polish independence, but others were afraid that they would upset the balance of power in Europe if they allowed Poland to become its own country again.
So the Polish Question was basically the debate over whether Poland should be allowed to be its own country, or whether it should remain divided up and controlled by Russia, Prussia, and Austria. It was a big political issue at the time and people had very strong opinions on both sides.