IPT (Autodesk Inventor part) is one of the native file formats of Autodesk Inventor, along with IAM (Autodesk Inventor assembly), IDW (Autodesk Inventor drawing), and IPN (Autodesk Inventor presentation). Assemblies consist of arrangements of parts.
Autodesk Inventor has a new major version every year, and it's documented that the assembly file format changes and requires updates to read newer files; it's not clear whether the part files are similarly incompatible from year to year.
IPT format is based on the "OLE2" document container format. The IPT files contain a file within the OLE container called "RSeDb". Furthermore the file contains sub directories with names RSeStorage, RSeEmbeddings an RefdFiles.