A VBX file is a custom control used in earlier versions of Visual Basic (VB) and other Windows development environments. These files contain reusable code components that extend the functionality of the development environment, allowing developers to easily incorporate pre-built features like custom user interface elements, data access tools, and specialized algorithms into their applications. VBX controls were a popular way to add features to VB applications without having to write all the code from scratch. They were essentially DLLs (Dynamic Link Libraries) specifically designed for use within the VB environment. The VBX standard was prevalent in the 16-bit Windows era (Windows 3.x) and provided a mechanism for third-party developers to create and distribute reusable components. While VBX controls offered significant advantages in terms of code reuse and rapid application development, they are now largely obsolete due to the transition to 32-bit and 64-bit Windows operating systems and the introduction of newer component technologies like ActiveX controls (OCX) and .NET assemblies. Modern versions of Visual Basic and other development environments no longer support VBX files.