Microstation is a Bentley trademark and provides not only for GIS graphical tools but has a wide range of products that have a large footprint in GIS and related areas. Sometimes abbreviated ustation there is a large legacy of MDL (Microstation Development Language) and VBA and more recently the ability to interact and build models using c#.
MicroStation™ is a 3D CAD platform owned and produced by Bentley Systems, Inc. It is used stand-alone as a 3D and 2D CAD tool. It is a base platform for other applications in the fields of plant design, architecture, engineering and GIS. Applications are developed by Bentley Systems. Third parties, such as LA Solutions Ltd, may join the Bentley Developer Network and create new applications that use MicroStation as a platform. Development possibilities are provided for several languages: VBA, MDL (a C-style API), the MicroStationAPI (a C++ API) and the DgnPlatformNet API. VBA is delivered with MicroStation. The other APIs are delivered in a separate SDK. To develop using those APIs, you must have both MicroStation and the SDK installed.