Alt-key codes
Alt symbols are special text characters and signs that you can write straight from your keyboard. You can type those symbols in if you know how to do that and know corresponding symbol codes.
Alt Codes
Make symbols!
Alt codes - are symbol-typing shortcuts for keyboards. It's available on computers running Windows OS.
Don't get sad if you are not on Windows. There also are special ways to type text symbols from keyboard on Mac and Linux.
Process
To produce alt symbols, press and hold Alt key and, while holding it, enter character's Alt code with your keyboard's numeric keypad. If you want more clearance on this, read my more detailed descriptions on Alt codes on PC keyboard and Alt codes on Laptop keyboards.

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