Simply put, the Performance Max is a one-size-fits-all campaign type that offers you all the Google Ads inventory and requires the least amount of work. You just need to provide up to 15 images, 5 logos, 5 headlines, 5 long headlines, 5 descriptions, and Google will do the rest. Then, its machine learning systems will automatically serve the responsive ads across those channels and using automated Smart Bidding based on the goal the advertiser sets. That means you don't need to design specialised ads for specific channels.