By combining them with the FN key youll get access to F1 - F12 keys which can be associated with particular application features useful in Photoshop for example. Typing math symbols into Word can be tedious. Release both keys then type capital O.
Or a combination of the OptionAlt key and the Shift key.
You can use the Character Viewer to add special characters and symbols to text such as math symbols Latin characters and pictographs. From the drop-down menu options choose Show Keyboard Viewer to open the utility. For Windows users whilst you press and hold the Alt key press the Approximately Equal symbol alt code which is 247 on the numeric keypad then release the alt key. The default way of doing it is to use the Insert Symbols More Symbols dialog where you can hunt for the symbol you want.