Steps to follow for running your app on browser, device or deploy as PWA.
Run the app on Browser
Once you have the initial setup done, it's time to run your app. First we'll run the app in development environment. In development environment, your app runs in a browser (of your choice). It is recommended to make all changes and development while running the app on browser . Running on device while developing will be too time consuming.
To run the app on browser, run
$ ionic serve
on your command line, inside your project folder. This will build the project and deploy it on a localhost url (usually it is localhost:8100).
The initial deploy process will take some time when it creates "chunks" of code pieces. Once you see compiled successfully , you are good to go. Your browser window will open automatically and load the app in a full screen view.
To change the app to a device view, right click anywhere on the browser and choose Inspect Elementand choose device mode.
More about browser development tools can be found out in following links