COM interface  

The way in which an object exposes its services externally to clients. A COM object provides an interface for each set of related methods and properties. Note that COM properties are not identical to properties on VCL objects. COM properties always use read and write access methods.  

COM server  

A module, either an EXE, DLL, or OCX, that contains the code for a COM object. Object implementations reside in servers. A COM object implements one or more interfaces.  

COM client  

The code that calls the interfaces to get the requested services from the server. Clients know what they want to get from the server (through the interface); clients do not know the internals of how the server provides the services. Delphi eases the process in creating a client by letting you install COM servers (such as a Word document or PowerPoint slide) as components on the Tool Palette. This allows you to connect to the server and hook its events through the Object Inspector.