Yes, web app send push notifications to desktop and mobile devices users. 

To send these browser push notifications, there are two ways you can do it.

First, you can set up your own notification platform. However, setting up your push notification platform requires time contribution and a lot of resources. 

The other best option is you can integrate existing push notifications softwares. The best push notification service availabe is Truepush for free. There are no limits on the number of push notifications or number of subscribers.

You can also set up your PWA push notification and AMP notification using Truepush.