What is the use of adding network in Siemens plc programming?

Generally, when writing a program, only one output is written in a network. The advantage is that the structure is simple and clear. Secondly, when you write a program with errors, you write a lot of programs in a network, and then compile through you. The software will prompt you for the wrong network;

If you only write one line of code in a network, it is easy to see the problem, but when you write a lot of programs in a network, it is not convenient to find the error!