ProgIDs are the human-readable equivalent of Microsoft COM CLSID values. There is a Win32 API to convert from one to the other (ProgIDFromCLSID). ProgIDs are what you pass to scripting applications to create COM objects.
Is this the "application name" tcom needs? Yes.
Example values:
InternetExplorer.Application
package require tcom set ie [tcom::ref createobject "InternetExplorer.Application"] $ie Visible 1 $ie Navigate http://www.tcl.tk/
See also "registry".