A project icon, or rather a project-file, often requires a tool to open it.
F.ex; A document written in a wordprocessor would be called a project,
whereas the wordprocessor is the tool/program that opens it.
This is a simplification as the textdocument could be opened in other programs too.
Within the project-icon, you can "associate" which tool should be used to open it.
I use 3rd party programs to change the type of file, so I can't give you an easy
way to change it.
Besides Projects and Tools, you also have Drawers (folders) and Trashcan as icon-types...
