The Alt key on a Mac is the third key from the left on the bottom row of the keyboard, and it is usually labeled as Option. The Alt key is used for many important things on a Mac, such as typing symbols and accent marks, changing the function of another key when used in combination, and as a modifier for menu options. The Alt key is also frequently pressed alongside other keys to activate program or system shortcuts. There are two Alt keys on a Mac keyboard, one to the left of the Command key on the left side of the spacebar, and the other to the right of the Command key on the right side of the spacebar. The reason there are two Alt keys is that the Alt key is used for lots of key combinations, and sometimes it’s easier to use the one on the left and, in other cases, the one on the right.