Blazor is a new web development framework that allows web applications to be built using C# instead of JavaScript. It uses WebAssembly, which compiles C# to a low-level assembly-like format that runs with native performance in web browsers. Blazor applications can run either on the client-side in the browser or server-side, and it provides advantages when working within the Microsoft ecosystem. The document discusses WebAssembly, provides a code example, and examines whether Blazor is being used in practice along with mentioning a Chilean company using it successfully for their PWA.