What does the quote from stettin on the baltic to trieste on the adriatic an iron curtain has descended across the continent mean?

Winston Churchill was talking about how suddenly Europe had been divided between the capitalist West, which was democratic and allied with the US, and the East which was largely made up of communist puppet states of the Soviet Union.

Stettin was a city in Germany. After the end of World War II, the border changed and it became a city in Poland, and was officially renamed Szczecin. Trieste is a city in the northeast corner of Italy.