ArcObjects

ArcObjects
[ESRI software] A library of software components that make up the foundation of ArcGIS. ArcGIS Desktop, ArcGIS Engine, and ArcGIS Server are all built using the ArcObjects libraries.

ArcObjects is the development platform for the ArcGIS suite of applications developed by ESRI, which includes ArcReader, ArcMap, ArcCatalog, ArcScene, ArcGlobe, and ArcGIS Server.

ArcObjects is a library of platform-independent software components, written in C++, that provides services to support GIS applications, ...

ArcGIS Explorer is a .Net desktop app based on a new lightweight ArcObjects library
The app is downloaded once from the server and installed locally (just as you would with Google Earth and others)
The server is the most important part of the system ...

See also: GIS, Software, Information, Model, Access