What should I put in an edit summary?

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. 

Minor edits

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.

Major edits

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.