Currently in Beta, Performance Max Campaigns are a new way to access all Google Ads inventory from a single campaign, investing your advertising dollars where the Conversion Opportunities are:

YouTube
Display
Search
Discover
Gmail
Maps

With the help of automation and Smart Bidding, it helps you maximize performance and deliver results against the goals that matter most to you using Target CPA or Target ROAS bidding strategies.

Main Objective & Secondary Conversion Goals
Define and manage which conversion actions you want to measure for each goal. Then, you prioritize each goal to use directly in your campaign optimizations and bidding.

Asset Groups Become the New Ad Group
Videos (at least 10 seconds long), standard display ads, responsive text ads, responsive display ads. Powered by URL Expansion / targeting like Dynamic Search Ads.

Audience Signals
Customer Match, Website Visitors & Customer Audiences guide automated targeting to help you unlock new related converting audience segments.

For more details, check out Google’s write up Achieve your goals across Google’s ad inventory with Performance Max!