"This web part demonstrates the following features: Adding a web part to a 'Full-Width' section, resizing the web part to fit the given space of the page, fetching dynamic parameters like the current theme or querystring and passing them to the IFrame."
"name":"Build your first SharePoint client-side web part",
"description":"Client-side web parts are client-side components that run in the context of a SharePoint page. Client-side web parts can be deployed to SharePoint environments that support the SharePoint Framework. You can also use modern JavaScript web frameworks, tools, and libraries to build them.",