OLE stands for Object Linking and Embedding (see Wikipedia), and COM stands for Component Object Model (see Wikipedia).

Type libraries

From Wikipedia:

Automation components are usually provided with type libraries, which contain metadata about classes, interfaces and other features exposed by an object library. Interfaces are described in Microsoft Interface Definition Language. Type libraries can be viewed using various tools, such as the Microsoft OLE/COM Object Viewer (oleview.exe, part of the Microsoft Platform SDK) or the Object Browser in Visual Basic (up to version 6) and Visual Studio .NET. Type libraries are used to generate Proxy pattern/stub code for interoperating between COM and other platforms, such as Microsoft .NET and Java.

Here's a link from Arnor Baldvinnson on creating type libraries using IDL (from the ArcGIS SDK documentation).