How to understand that our newly created shopify app is made in shopify app bridge 2.0

[hasrat]

I am new to Shopify App Development and trying to understand the need of App Bridge. I created an shopify app codeigniter PHP framework and enabled embedding, I was able to see my app in the Shopify Admin without doing anything for the App Bridge. If I can see the app in admin whats the need to App Bridge.
Can you please help me understand the need of app bridge ?

[KfirS]

Sure.

App Bridge is a javascript library that enables interaction between your embedded app (that is rendered in an iframe) and the Shopify admin.

Using app bridge you can activate native Shopify UI behaviors. such as different dialogs, notifications, toolbar actions, etc. You will also need it to authenticate specific store users (get online tokens) and get the current user session token for authenticating your server.