Welcome! They always shake hands as a sign of respect. At least, this is what happens at the beginning of the game. When they do so at the end, it is usually a sign of surrender. In this case, you can see how Alexander surrenders and shakes hands with Vladislav. He could have stopped the clock, knocked down his king or simply said that he surrenders. When you accept a draw you also shake hands as if you are closing a deal. In the case of electronic boards, you can also know the result by seeing where they place their kings in the center of the board after the game. Here, both kings end up on white squares and the computer automatically detects victory for White. 🤝🤝🤝🤝🤝