Let's look at what happens if you see someone has made an edit to an article you're working on.

You can see how an article has evolved over time by clicking the "View history" link at the top of every article.

On the "View history" page, you'll see a list of recent changes to the article, with edit summaries describing what other editors have done.

In this example, on the page for Nellie Bly, you'll see that on July 15, an editor made a change to the "Asylum expose" section of her article. Others left more detailed descriptions. Tom Streissguth added a link to an online collection of Bly's newspaper articles, while CutOffTies removed an unsourced claim. What if you'd like to see what that unsourced claim was?

You can compare histories between articles by clicking on the radio buttons next to each line:

Then select the "compare history" button at the top.