U+2325 Option Key

The Wikipedia has the following information about this codepoint:

The Option key, ⌥, is a modifier key present on Apple keyboards. It is located between the Control key and the Command key on a typical Mac keyboard. There are two Option keys on modern (as of 2020) Mac desktop and notebook keyboards, one on each side of the space bar. (As of 2005, some laptops had only one, in order to make room for the arrow keys.)

Apple commonly uses the symbol U+2325 ⌥ OPTION KEY to represent the Option key. From 1980 to 1984, on the Apple II, this key was known as the closed apple key or the solid apple key, and had a black line drawing of a filled-in apple on it.

Since the 1990s, "Alt" has sometimes appeared on the key as well, for use as an Alt key with non-Mac software, such as Unix and Windows programs; as of 2017, the newest Apple keyboards such as the Magic Keyboard no longer include the "Alt" label. The Option key in a Mac operating system functions differently from the Alt key under other Unix-like systems or Microsoft Windows. It is not used to access menus or hotkeys but is instead used as a modifier for other command codes, as well as to provide easier access to various accents and symbols. In this regard, it is akin to the AltGr key, found on some IBM-compatible PC keyboards.