Hot Reload for .Net is a new feature in .NET 6 that facilitates fast, fluid, dynamic, and productive web development and testing. It does all this by allowing you to make changes to your web application's code and immediately see those changes without restarting or rebuilding the application. The changes get patched in your running application.
One thing I have noticed in using this feature is that my cascading style sheet changes are not always seen when using the Hot Reload feature. Sometimes refreshing the browser will make the hot reload work. I am assuming this problem is due to how browsers like Chrome caches CSS files.
Here is an excellent excerpt from a video that demonstrates the Hot Reload feature.