System.Net.Http is a namespace in the .NET framework that provides classes for sending HTTP requests and receiving HTTP responses. It simplifies the process of interacting with web services and APIs, allowing developers to easily make GET, POST, PUT, and DELETE requests. This namespace is essential for applications that need to communicate over the internet. The primary class in this namespace is HttpClient, which is designed to be reused for multiple requests, improving performance and resource management. It supports asynchronous operations, making it suitable for modern applications that require non-blocking I/O operations when dealing with web resources.