Visually, web push notifications (classic push) and in-page push notifications (IPP or floating push notifications) look similar: those are the ads that appear in the corner of your browser. The main difference is that classic pushes require an initial subscription from the user to get displayed, while in-page ones are placed directly on the website. Classic push is OS-based, while IPP is browser-based. IPP appears to any user currently on the website, therefore this type of ad does not require a subscription.