Apple recently introduced and presented Web Push, a new Web Kit tool permitting to send notifications to users on your websites and web apps. However, push notifications have been a thing on macOS since Mavericks. Therefore, what is the difference between these two things ?(https://developer.apple.com/notifications/safari-push-notifications/ ) and that new thing (https://developer.apple.com/videos/play/wwdc2022/10098/)
The difference is that you don't need any Developer account or APNS Certificates to use the Web Push API, which has always been the case for desktop Notifications as well as iOS Push Notifications.
When they say it's "really" push, they mean they're switching to the open standard 'Web Push API' which Chrome and Firefox etc. have been using for a while.
You can then set up a nodeJS server (or equivalent) to send out alert notifications to (almost) any browser. (Once macOS Ventura comes out with Safari 16).