ASP.NET is a web application framework developed by Microsoft for building modern, dynamic, and secure web applications. It supports a variety of programming languages like C# and VB.NET and offers features such as web forms, MVC architecture, and APIs for seamless integration with databases and other services. ASP.NET integrates well with Microsoft SQL Server for database operations, providing high performance and ease of use. It includes features like data binding, state management, and security tools, making it a comprehensive solution for developing scalable web applications.