@marito74, clean code is essential to help developers understand each other. A good example is well-organized content with an awesome markdown applied to it.

If you check the two images above, the second image has the sentences in green. Those are comments in in PHP, which are highlighted in green. Comment helps to give a description of the block of code below. Adding descriptive and meaningful comments helps another developer have a better understanding of the block of code below. So that is a clean-up as compared to the previous case, where I did not add a comment.