Specific to this example:

1 and Zhang San are bulls, expecting soybean prices to rise and buying positions at the same time;

Li Si is a short-seller, expecting soybean prices to fall, and at the same time selling positions.

2, bulls and bears are relative, such as:

A month later, when the soybean price rose to 2.2 yuan/Jin, Zhang San predicted that the soybean price would not rise again and sold his position. At this time, Zhang San became an empty position.

Do you understand?