Below the editor window of a page there is another input field for the summary of your changes. In this field you should briefly describe what you have changed in the article of the page and, if possible, also indicate the sources of newly added information.
Therefore, please always add a summary to your changes. Because even a bad summary is better than none at all!
The purpose of summaries is to make it easy for others to see what has been changed, and to make it uninteresting for them to check the changes in detail. If you also include Help:Sources for your changes, you make it easier for other authors to understand where you got the new information. This can save you and others unnecessary discussions about certain information.
Where does the summary appear?
If you have described your changes in a summary, this is automatically displayed in the version history. Here you can track all changes made to this page and undo them if necessary.