Okay, so let's say you know how to play a game, right? Imagine that game is like a battle or a war, where two sides are trying to beat each other. In this particular game, one side is called the Germans and the other side is called the Soviet Union.
Now, the game takes place in a very cold area, and the players have to deal with things like snow and ice. The first time they played the game, the Germans were trying to win and they did pretty well - they took control of a lot of the area.
But then, a little while later, the game started up again - this time, it was called the second winter campaign. See, the Soviet Union didn't want to give up, even though the Germans had taken a lot of their land.
During the second winter campaign, the players had to be even more careful because it was colder and there was a lot of snow on the ground. Both sides had to make new plans and come up with new strategies to try and beat the other side.
In the end, the Soviet Union actually did better in this second round of the game - they were able to take back some of the land that they had lost the first time around.
So, that's basically what the second winter campaign was - just another round of a big game where two sides were trying to win in a snowy, cold area.