DotNet Core is an open-source, cross-platform framework developed by Microsoft for building modern applications. It allows developers to create applications that can run on various operating systems, including Windows, macOS, and Linux. This flexibility makes it a popular choice for web, mobile, and cloud-based applications. One of the key features of DotNet Core is its modular architecture, which enables developers to include only the necessary components for their applications. This results in smaller, more efficient applications. Additionally, DotNet Core supports multiple programming languages, including C# and F#, making it accessible to a wide range of developers.