Alt "is also called change key and replacement key, because it is the abbreviation of the English word" Alternative ",which is often used in combination with other keys. Without a mouse, you can easily open the menu of the software with the "Alt" key. As we all know, Alt keys are left and right on the keyboard. In an American keyboard, the left and right keys have the same function. But, you know what? On most European keyboards, the "Alt" key on the right is labeled as "Alt Gr", which is similar to the shift key-pressing the Shift key and the letter key at the same time can select uppercase or lowercase.