Android SDK has a nifty configurable UI widget where in you can load websites within the app itself. The widget is called WebView. WebView is a UI widget just like any other UI view (Button/ TextView etc.) which can be placed or sized however you want in your layout. It is like an embedded mini browser in your app that can load any website you want
Perhaps the most frequent architecture that a lot of companies follow is that they have a web service and use an app/website as a front end. Take an example of taxi app like Uber. They have an app for making booking, payments, cancellations etc. and a backend web service which facilitates all of this. The app programmatically connects to their web service through the internet and exchanges data to and fro as required.
There are some free to use web services that your application can use to display information. For example, Open Weather API is a web service that provides data for you to use.
There are some libraries that allow you to connect to the internet and use web services. The most popular one and widely used library for Android is Retrofit. Retrofit is an open source and easy to use library.
The following resource will help you set it up and show how to use it
