what is the equivalent of the alt key on a mac
Alt key On a Macintosh, the Alt key is called the Option key. It is not used to enter numeric character codes. Instead, keyboard letters and numbers are used. The diagram below shows the special characters a US Mac keyboard will produce when the Option key is pressed.[1]
Alt key Since the 1990s Alt has been printed on the Option key on most Mac keyboards. Alt is used in non-Mac software, such as non-macOS Unix and Windows programs, but in macOS it is always referred as the Option key. The Option key's behaviour in macOS differs slightly from that of the Windows Alt key (it is used as a modifier rather than to access pull-down menus, for example).
Keyboard layout Instead of the Alt and AltGr keys, Apple Keyboards have ⌘ Cmd (command) and ⌥ Option keys. The ⌥ Option key is used much like the AltGr, and the ⌘ Cmd key like the Ctrl on IBM PCs, to access menu options and shortcuts. Macs have a Ctrl key for compatibility with programs that expect a more traditional keyboard layout. It is especially useful when using a terminal, X11 (a Unix environment included with OS X as an install option) or MS Windows. The key can generally be used to produce a secondary mouse click as well. There is also a Fn key on modern Mac keyboards, which is used for switching between use of the F1, F2, etc. keys either as function keys or for other functions like media control, accessing dashboard widgets, controlling the volume, or handling exposé. Fn key can be also found on many IBM PC laptops, where it serves a similar purpose.
Command key On a keyboard made with the Microsoft Windows logo, the Windows keys are identical in function to the Mac Command keys, as is the [[Meta key|â—† Meta]] key on a Sun or another Unix-oriented keyboard.[18] Conversely, when an Apple USB keyboard is used with other operating systems, the Command keys function as Windows keys or Meta keys.