Link goes to a page with a minimal hint and a video.

Their blog post has some detail: https://blog.google/technology/google-labs/pomelli/

Kagi said the "Key features and functionalities of Pomelli include:

    Content Generation: Pomelli can generate various marketing assets 
    such as social posts and ad creatives by analyzing
    a company's website to understand its brand identity
    
    Brand DNA: The tool builds a "Business DNA" from a company's 
    website to ensure generated content is consistent with the brand's identity

    Campaign Creation: It aims to generate entire on-brand marketing 
    campaigns with minimal user input

    Editable Assets: The generated campaign assets are editable

    Canva Alternative: Pomelli is positioned as a competitor
    to design tools like Canva"