On Adwords, advertisers can´t really edit ads. When advertisers edit an ad and save it, Adwords create a new version of the ad. Version history of the ads lets advertisers go back and see previous versions of the ad, as well as data on how those ads performed.
Version history is available in Ads & extensions. On the pencil icon Edit to the right of your ad: See version history.
According to Adwords, version history includes the dates each version was edited, how long that version was in place for, and what changed. The information about how long the version was in place can include review periods or periods where the ad wasn’t showing, for example, because it was paused. A CSV report is available.
Google recommends testing different versions of an ad. Adwords automatically shows better-performing ads more often by default.