An edit summary is a brief explanation of an edit to a Wikipedia page. Summaries help other editors by (a) saving the time to open up the edit to find out what it's all about, (b) providing a reason for the edit, and (c) providing information about the edit on diff pages and lists of changes (such as page histories and watchlists).
|This page in a nutshell: When editing, be sure to summarize your contributions.|
The Wikipedia community strongly encourages editors to provide meaningful edit summaries. To add a summary, type in the text entry field in the Edit summary box located near the bottom of the Editing page. The box looks like this: