That's right, Ashley .
Some companies like Steam, EA Origin, AVG, Kaspersky, Unity and GameHouse frequently call the traditional Windows apps as PC apps alongside Mac apps which called Mac apps and Linux apps which called Linux apps (PC/Mac/Linux).
But as I look at Steam's game system requirements:
- PC games need a Windows OS.
- Mac games need an OS X.
- Linux games need an Ubuntu OS.
So, my thoughts is Windows is an OS for PCs and OS X is an OS for Macs.
But Ubuntu is an OS for both Windows and Linux PCs.
So Steam and other companies should mean both Windows and Linux platform as PC.
If some of my thoughts are wrong, tell me.