Update README for Components directory (#27650)

* Update README for Components directory

* Update src/Components/README.md

Co-authored-by: Pranav K <prkrishn@hotmail.com>

* Address feedback from peer review

* Use new top-level references for build

Co-authored-by: Pranav K <prkrishn@hotmail.com>

Author: captainsafia

src/Components/README.md

@@ -1,17 +1,53 @@
 # Blazor
 
-**Build modern, interactive web-based UIs with C# and Razor.**
+Blazor is a framework for building modern, interactive web-based UIs with C# and Razor. For more information on using Blazor to build apps, check out [the official docs](https://blazor.net).
 
-This folder contains the underlying *components* programming model that powers both server-side and client-side [Blazor](#blazor) applications.
+## Description
 
-Blazor is a component based web UI framework. Blazor apps can run client-side in browser on WebAssembly or server-side as part of an ASP.NET Core app. Blazor is a full single-page application (SPA) framework inspired by the latest JavaScript SPA frameworks, featuring support for offline/PWA applications, app size trimming, and browser-based debugging.
+This folder contains the component model shared between the WebAssembly and Server hosting models for Blazor.
 
-Blazor uses only the latest web standards. No plugins or transpilation needed. It runs in the browser on a real .NET runtime implemented in [WebAssembly](http://webassembly.org) that executes normal .NET assemblies.
+The following contains a description of each sub-directory in the `Components` directory.
 
-[![Gitter](https://badges.gitter.im/aspnet/blazor.svg)](https://gitter.im/aspnet/blazor?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge)
+- `Analyzers`: Contains a collection of Rosyln analyzers for Blazor components
+- `Authorization`: Contains source files associated with auth-related components and services in Blazor
+- `Components`: Contains the implementation for the Blazor component model
+- `Forms`: Contains source files for Form components in Blazor
+- `Ignitor`: A library for testing Blazor Server apps
+- `Samples`: Contains a collection of sample apps in Blazor
+- `Server`: Contains the implementation for Blazor Server-specific components
+- `Shared`: Contains a collection of shared constants and helper methods/classes
+- `Web`: Contains source files for handling DOM events, forms, and other components
+- `Web.JS`: Contains the source files for Blazor's client-side JavaScript
+- `WebAssembly`: Contains the implementation for WebAssembly-specific components
+  - `Authentication.Msal`: Contains the implementation for MSAL (Microsoft Authentication Library) auth in WASM applications
+  - `DevServer`: Contains the implementation for the Blazor dev server
+  - `JSInterop`: Contains the implementation for methods that allow invoking JS from .NET code
+  - `Sdk`: Contains the MSBuild definitions for the Blazor WASM SDK
+  - `Server`: Contains the implementation for WASM-specific extension methods and the launch logic for the debugging proxy
+  - `WebAssembly`: Contains WebAssembly-specific implementations of the renderer, HostBuilder, etc.
+  - `WebAssembly.Authentication`: Contains the WASM-specific implementations
 
-You can learn more about Blazor at https://blazor.net.
+## Development Setup
 
-## Getting Started
+### Build
 
-To get started with Blazor and build your first web app check out our [getting started guide](https://go.microsoft.com/fwlink/?linkid=870449).
+To build this specific project from source, you can follow the instructions [on building a subset of the code](https://github.com/dotnet/aspnetcore/blob/master/docs/BuildFromSource.md#building-a-subset-of-the-code).
+
+### Test
+
+This project contains a collection of unit tests implemented with XUnit and E2E tests implemented using Selenium. In order to run the E2E tests, you will need to have Selenium installed on your machine.
+
+The E2E tests are located in the top-level `tests` folder in this directory. The E2E tests consists of a top-level `TestServer` which instantiates different app servers for specific scenarios:
+
+- Standalone Blazor WASM
+- Hosted Blazor WASM
+- Blazor Server
+- Blazor Server with pre-rendering
+
+Each app server mounts the same `BasicTestApp` application under each scenario.
+
+To run the tests for this project, you can [run the tests on the command line](https://github.com/dotnet/aspnetcore/blob/master/docs/BuildFromSource.md#running-tests-on-command-line) in this directory.
+
+## More Information
+
+For more information, see the [ASP.NET Core README](../../README.md).