purpose of vertical bar in programming IDEs/Editors

Question

In this example. I'm using Phpstorm Code Editor and I wonder the purpose of this Vertical Bar

Answer 1

This is a visual limiter of the line length. Usually the code convention in programming languages or in particular project requires to have the line of code to be limited by length.
For example Python's PEP 8 coding convention requires it to be limited to 79 characters. So basically this limiter in your text editor or IDE is just made for convenience to help you to control the maximum line length in your code. Usually you can set-up the maximum code line length in the settings.