An edit summary is a brief explanation of an edit to a Wiki page.
After you click Save page on the top left part of the page, a summary window will appear:
When you make an edit, major or minor, it’s a best practice to put at least a single word description in the Summary text box.
If you are making minor changes such as spelling corrections, formatting, and minor rearrangement of text, check the This is a minor edit box. This means that anyone watching the document does not receive a notification of the change.
Marking a significant change as a minor edit is considered bad Wiki etiquette, especially if it involves the deletion of some text. If you have accidentally marked an edit as minor, a best practice is to edit the page again and uncheck the box for This is a minor edit. Then, in the summary state that the previous change was a major one.
Before engaging in a major edit, you might wish to consider discussing proposed changes on the article discussion/talk page.
Once the edit has been completed, make sure you include a summary of the edit stating that you made a major change, and describe the nature of those changes.