Same keyboard, different names. Apple prints symbols in its menus instead of words; this is the decoder.

Windows keyMac keySymbolWhere it sits, what it does
Ctrl CommandNext to the space bar, where Alt is on a PC. Does what Ctrl did: ⌘C copies, ⌘S saves.
Alt OptionBetween Ctrl and ⌘. Types special characters and modifies clicks and menu items.
Win CommandOn a PC keyboard plugged into a Mac, the Win key is ⌘ and Alt is ⌥.
Ctrl (the real one) ControlFar left. Rarely used outside Terminal, where ⌃C still cancels a command.
Shift ShiftSame.
Backspace DeleteLabelled "delete", works like Backspace.
DeletefnLaptops have no forward-delete key: hold fn and press delete.
Enter ReturnSame key. In Finder it renames a file instead of opening it.
Home / End / Line start and end. The Home and End keys themselves scroll the document.
PgUp / PgDnfn / fn⇞ ⇟fn plus the arrows on laptops.
PrtSc3Whole screen to a file. ⌘⇧4 selects an area, ⌘⇧5 opens the screenshot toolbar.
F1 to F12F1 to F12Brightness, volume and media by default; hold fn for the function key, or switch them in System Settings.
InsertnoneDoes not exist on a Mac.

Menu symbols, in the order they appear in a Mac menu: ⌃ Control, ⌥ Option, ⇧ Shift, ⌘ Command. "⇧⌘S" means hold Shift and Command, press S.