Users see notifications on mobile as well as on Desktop in salesforce. This is a great way to provide real-time notification to Sales and Services rapes about new leads, cases or updates on cases or opportunities. You can set up a new Bell/push notification just in a few steps. Here are steps to set up.
Step 1: Create the Notification Route:- You create notification route to use in process builder to route notification either to mobile app or desktop or both

Step 2: Create the Process Builder :- Process builder is to trigger notification. You define object and criteria to trigger notification. In my case i need to setup notification for the case owner whenever a new case is created. Following steps below
- Go to Setup → Process Builder → Create new :- Give Name and select Object and add relevant criteria.
- Add Immediate Action and select ‘Send custom Notification’ Action Type drop-down


Testing:- Activate process builder. Now in my case whenever a new case is created. Owner is getting push notifications on his Salesforce1 mobile app and one desktop bell icon.

Author: Swapnil Jain, Salesforce Developer