The search that David points you to will show all of the various extensions used by ArchiCAD.
If by 'expansion', you mean "What does PLP stand for?" - then I'm not sure.
PLN is usually read as 'PLaN', for a solo project.
PLA is a project archive (or PLan Archive).
How PLP becomes a teamwork file and PLC becomes a teamwork draft, I'm not sure ... perhaps the P and C mean something in Hungarian?
Cheers,
Karl
AC 28 USA and earlier • macOS Sequoia 15.2, MacBook Pro M2 Max 12CPU/30GPU cores, 32GB
One of the forum moderators