A .csx file is a C# script file used primarily within the .NET ecosystem, specifically designed for the Roslyn scripting engine. Unlike standard .cs files, which require a full project compilation process including a solution or project file, .csx files are intended to be executed as standalone scripts. They allow developers to write C# code that can be interpreted and run on-the-fly, making them ideal for automation tasks, quick prototyping, data processing, or configuration scripts. The format supports the inclusion of NuGet packages via directives, allowing for external library dependencies to be resolved dynamically. These files are heavily utilized in environments like Azure Functions for serverless computing, where they provide a lightweight way to define function logic without the overhead of a full compiled assembly. Because they are interpreted, they offer a more flexible, 'scripting-like' experience while maintaining the strong typing and performance benefits of the C# language.