It’s a Russian special wooden carved window frame decorations. They also can be seen on territories that belonged to the Russian Empire or USSR or not far from there.
In Russian architectural schools, we call “nalichnik” every window decor but its local word that first, it meant wooden carving and later everything else.
They can be seen in most of Russian towns, cities, and villages. But only a couple of examples in Moscow and St.-Petersburg. In Moscow, most of the wooden buildings were replaced long ago, but in St.-Petersburg they just weren’t built cause it was developed western styled and all houses were made of brick or stone.