Alt Gr
Short for Alt(ernative) Graphic. Key used for additional keyboard character.
You can get the Euro sign in Windows by pressing AltGr+e.
Alt Gr
Same as above but the Euro sign (€) is actualy done by pressing Alt Gr and 4. (The 4 with the dollar sign $ above it on the main keypad )
To make an Euro sign you must press: Alt Gr + 4 = €